* Add a primop to return the context of a string.

* In string contexts containing derivations
(e.g. "${somePkg}/bin/foo"), store the original derivation expression in the context.
2010-01-31 20:54:44 +00:00 · 2010-01-31 20:08:57 +00:00 · 2010-01-31 20:06:58 +00:00 · 2010-01-29 12:22:58 +00:00 · 2010-01-29 11:53:58 +00:00 · 2010-01-25 17:18:44 +00:00
84 changed files with 1339 additions and 2046 deletions
--- a/Makefile.am
+++ b/Makefile.am
@@ -29,11 +29,9 @@ init-state:
 	$(INSTALL) $(INIT_FLAGS) -d $(DESTDIR)$(localstatedir)/nix/profiles
 	$(INSTALL) $(INIT_FLAGS) -d $(DESTDIR)$(localstatedir)/nix/gcroots
 	$(INSTALL) $(INIT_FLAGS) -d $(DESTDIR)$(localstatedir)/nix/temproots
-	$(INSTALL) $(INIT_FLAGS) $(GROUP_WRITABLE) -d $(DESTDIR)$(localstatedir)/nix/gcroots/tmp
-	$(INSTALL) $(INIT_FLAGS) $(GROUP_WRITABLE) -d $(DESTDIR)$(localstatedir)/nix/gcroots/channels
 	ln -sfn $(localstatedir)/nix/profiles $(DESTDIR)$(localstatedir)/nix/gcroots/profiles
 	$(INSTALL) $(INIT_FLAGS) -d $(DESTDIR)$(localstatedir)/nix/userpool
-	$(INSTALL) $(INIT_FLAGS) -m 1777 -d $(DESTDIR)$(storedir)
+	-$(INSTALL) $(INIT_FLAGS) -m 1777 -d $(DESTDIR)$(storedir)
 	$(INSTALL) $(INIT_FLAGS) $(GROUP_WRITABLE) -d $(DESTDIR)$(localstatedir)/nix/manifests
 	ln -sfn $(localstatedir)/nix/manifests $(DESTDIR)$(localstatedir)/nix/gcroots/manifests

--- a/configure.ac
+++ b/configure.ac
@@ -55,7 +55,7 @@ test "$localstatedir" = '${prefix}/var' && localstatedir=/nix/var
 # except that it requires the ATerm "lib" directory to be in $PATH, as
 # Windows doesn't have anything like an RPATH embedded in executable.
 # Since this is kind of annoying, we use static libraries for now.
-    
+
 AC_ARG_ENABLE(static-nix, AC_HELP_STRING([--enable-static-nix],
  [produce statically linked binaries]),
  static_nix=$enableval, static_nix=no)
@@ -63,19 +63,25 @@ AC_ARG_ENABLE(static-nix, AC_HELP_STRING([--enable-static-nix],
 if test "$sys_name" = cygwin; then
   static_nix=yes
 fi
-  
+
 if test "$static_nix" = yes; then
    AC_DISABLE_SHARED
    AC_ENABLE_STATIC
 fi

-  
+
 # Windows-specific stuff.
 if test "$sys_name" = "cygwin"; then
    # We cannot delete open files.
    AC_DEFINE(CANNOT_DELETE_OPEN_FILES, 1, [Whether it is impossible to delete open files.])
 fi

+# Solaris-specific stuff.
+if test "$sys_name" = "sunos"; then
+    # Solaris requires -lsocket -lnsl for network functions
+    ADDITIONAL_NETWORK_LIBS="-lsocket -lnsl"
+    AC_SUBST(ADDITIONAL_NETWORK_LIBS)
+fi

 AC_PROG_CC
 AC_PROG_CXX
@@ -88,8 +94,7 @@ AC_PROG_LIBTOOL


 # Use 64-bit file system calls so that we can support files > 2 GiB.
-CFLAGS="-D_FILE_OFFSET_BITS=64 $CFLAGS"
-CXXFLAGS="-D_FILE_OFFSET_BITS=64 $CXXFLAGS"
+AC_SYS_LARGEFILE


 # Check for pubsetbuf.
@@ -140,7 +145,6 @@ NEED_PROG(bash, bash)
 NEED_PROG(patch, patch)
 AC_PATH_PROG(xmllint, xmllint, false)
 AC_PATH_PROG(xsltproc, xsltproc, false)
-AC_PATH_PROG(jing, jing, false) # needed because xmllint --relaxng seems broken
 AC_PATH_PROG(w3m, w3m, false)
 AC_PATH_PROG(flex, flex, false)
 AC_PATH_PROG(bison, bison, false)
@@ -189,31 +193,6 @@ AC_ARG_WITH(store-dir, AC_HELP_STRING([--with-store-dir=PATH],
  storedir=$withval, storedir='/nix/store')
 AC_SUBST(storedir)

-AC_ARG_ENABLE(old-db-compat, AC_HELP_STRING([--disable-old-db-compat],
-  [disable support for converting from old Berkeley DB-based Nix stores]),
-  old_db_compat=$enableval, old_db_compat=yes)
-AM_CONDITIONAL(OLD_DB_COMPAT, test "$old_db_compat" = "yes")
-
-AC_ARG_WITH(bdb, AC_HELP_STRING([--with-bdb=PATH],
-  [prefix of Berkeley DB (for Nix <= 0.11 compatibility)]),
-  bdb=$withval, bdb=)
-AM_CONDITIONAL(HAVE_BDB, test -n "$bdb")
-if test -z "$bdb"; then
-  bdb_lib='-L${top_builddir}/externals/inst-bdb/lib -ldb_cxx'
-  bdb_include='-I${top_builddir}/externals/inst-bdb/include'
-else
-  bdb_lib="-L$bdb/lib -ldb_cxx"
-  bdb_include="-I$bdb/include"
-fi
-if test "$old_db_compat" = "no"; then
-  bdb_lib=
-  bdb_include=
-else
-  AC_DEFINE(OLD_DB_COMPAT, 1, [Whether to support converting from old Berkeley DB-based Nix stores.])
-fi
-AC_SUBST(bdb_lib)
-AC_SUBST(bdb_include)
-
 AC_ARG_WITH(aterm, AC_HELP_STRING([--with-aterm=PATH],
  [prefix of CWI ATerm library]),
  aterm=$withval, aterm=)
@@ -260,7 +239,7 @@ else
  bzip2_include="-I$bzip2/include"
  bzip2_bin="$bzip2/bin"
  bzip2_bin_test="$bzip2/bin"
-fi   
+fi
 AC_SUBST(bzip2_lib)
 AC_SUBST(bzip2_include)
 AC_SUBST(bzip2_bin)
@@ -285,7 +264,7 @@ AC_CHECK_FUNCS([strsignal])
 AC_CHECK_FUNCS([posix_fallocate])


-# This is needed if ATerm, Berkeley DB or bzip2 are static libraries,
+# This is needed if ATerm or bzip2 are static libraries,
 # and the Nix libraries are dynamic.
 if test "$(uname)" = "Darwin"; then
    LDFLAGS="-all_load $LDFLAGS"
--- a/doc/manual/Makefile.am
+++ b/doc/manual/Makefile.am
@@ -6,7 +6,12 @@ XSLTPROC = $(xsltproc) $(xmlflags) \
 --param xref.with.number.and.title 1 \
 --param toc.section.depth 3 \
 --param admon.style \'\' \
- --param callout.graphics.extension \'.gif\'
+ --param callout.graphics.extension \'.gif\' \
+ --param contrib.inline.enabled 0
+
+dblatex_opts = \
+ -P doc.collab.show=0 \
+ -P latex.output.revhistory=0

 # Note: we use GIF for now, since the PNGs shipped with Docbook aren't
 # transparent.
@@ -29,13 +34,9 @@ MANUAL_SRCS = manual.xml introduction.xml installation.xml \
 conf-file.xml release-notes.xml \
 style.css images

+# Note: RelaxNG validation requires xmllint >= 2.7.4.
 manual.is-valid: $(MANUAL_SRCS) version.txt
-#	$(XMLLINT) --xinclude $< | $(XMLLINT) --noout --nonet --relaxng $(docbookrng)/docbook.rng -
-	if test "$(jing)" != "false"; then \
-		$(XMLLINT) --xinclude $< | $(jing) $(docbookrng)/docbook.rng /dev/fd/0; \
-	else \
-		echo "Not validating."; \
-	fi
+	$(XMLLINT) --noout --nonet --xinclude --noxincludenode --relaxng $(docbookrng)/docbook.rng $<
 	touch $@

 version.txt:
@@ -50,7 +51,7 @@ manual.html: $(MANUAL_SRCS) manual.is-valid images

 manual.pdf: $(MANUAL_SRCS) manual.is-valid images
 	if test "$(dblatex)" != ""; then \
-		$(dblatex) manual.xml; \
+		$(dblatex) $(dblatex_opts) manual.xml; \
 	else \
 		echo "Please install dblatex and rerun configure."; \
 		exit 1; \
--- a/doc/manual/builtins.xml
+++ b/doc/manual/builtins.xml
@@ -324,6 +324,16 @@ x: x + 456</programlisting>
  </varlistentry>

  
+  <varlistentry><term><function>builtins.intersectAttrs</function>
+  <replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
+
+    <listitem><para>Return an attribute set consisting of the
+    attributes in the set <replaceable>e2</replaceable> that also
+    exist in the set <replaceable>e1</replaceable>.</para></listitem>
+
+  </varlistentry>
+        
+    
  <varlistentry><term><function>builtins.isAttrs</function>
  <replaceable>e</replaceable></term>

--- a/doc/manual/conf-file.xml
+++ b/doc/manual/conf-file.xml
@@ -233,7 +233,17 @@ build-use-chroot = /dev /proc /bin</programlisting>
    <filename>configure</filename> at build time.</para></listitem>

  </varlistentry>
-  
+
+
+  <varlistentry><term><literal>fsync-metadata</literal></term>
+
+    <listitem><para>If set to <literal>true</literal>, changes to the
+    Nix store metadata (in <filename>/nix/var/nix/db</filename>) are
+    synchronously flushed to disk.  This improves robustness in case
+    of system crashes, but reduces performance.  The default is
+    <literal>false</literal>.</para></listitem>
+
+  </varlistentry>
    
 </variablelist>

--- a/doc/manual/installation.xml
+++ b/doc/manual/installation.xml
@@ -107,13 +107,6 @@ you can use <command>configure</command>'s
 <option>--with-aterm</option> and <option>--with-bzip2</option>
 options to point to their respective locations.</para>

-<para>If you want to be able to upgrade Nix stores from before version
-0.12pre12020, you need Sleepycat's Berkeley DB version version 4.5.
-(Other versions may not have compatible database formats.).  Berkeley
-DB 4.5 is included in the Nix source distribution.  If you do not need
-this ability, you can build Nix with the
-<option>--disable-old-db-compat</option> configure option.</para>
-
 </section>


@@ -140,16 +133,25 @@ $ ./bootstrap</screen>
 <para>The installation path can be specified by passing the
 <option>--prefix=<replaceable>prefix</replaceable></option> to
 <command>configure</command>.  The default installation directory is
-<filename>/nix</filename>.  You can change this to any location you
-like.  You must have write permission to the
+<filename>/usr/local</filename>.  You can change this to any location
+you like.  You must have write permission to the
 <replaceable>prefix</replaceable> path.</para>

-<warning><para>It is best <emphasis>not</emphasis> to change the
-installation prefix from its default, since doing so makes it
-impossible to use pre-built binaries from the standard Nixpkgs
-channels.</para></warning>
+<para>Nix keeps its <emphasis>store</emphasis> (the place where
+packages are stored) in <filename>/nix/store</filename> by default.
+This can be changed using
+<option>--with-store-dir=<replaceable>path</replaceable></option>.</para>

-<para>If you want to rebuilt the documentation, pass the full path to
+<warning><para>It is best <emphasis>not</emphasis> to change the Nix
+store from its default, since doing so makes it impossible to use
+pre-built binaries from the standard Nixpkgs channels — that is, all
+packages will need to be built from source.</para></warning>
+
+<para>Nix keeps state (such as its database and log files) in
+<filename>/nix/var</filename> by default.  This can be changed using
+<option>--localstatedir=<replaceable>path</replaceable></option>.</para>
+
+<para>If you want to rebuild the documentation, pass the full path to
 the DocBook RELAX NG schemas and to the DocBook XSL stylesheets using
 the
 <option>--with-docbook-rng=<replaceable>path</replaceable></option>
@@ -160,27 +162,26 @@ options.</para>
 </section>


-<section><title>Installing from RPMs</title>
+<section><title>Installing a binary distribution</title>

-<para>RPM packages of Nix can be downloaded from <link
-xlink:href="http://nixos.org/" />.  These RPMs should work for most
-fairly recent releases of SuSE and Red Hat Linux.  They have been
-known to work work on SuSE Linux 8.1 and 9.0, and Red Hat 9.0.  In
-fact, it should work on any RPM-based Linux distribution based on
-<literal>glibc</literal> 2.3 or later.</para>
-
-<para>Once downloaded, the RPMs can be installed or upgraded using
-<command>rpm -U</command>.  For example,
+<para>RPM and Deb packages of Nix for a number of different versions
+of Fedora, openSUSE, Debian and Ubuntu can be downloaded from <link
+xlink:href="http://nixos.org/" />.  Once downloaded, the RPMs can be
+installed or upgraded using <command>rpm -U</command>.  For example,

 <screen>
-$ rpm -U nix-0.5pre664-1.i386.rpm</screen>
+$ rpm -U nix-0.13pre18104-1.i386.rpm</screen>
+
+Likewise, for a Deb package:
+
+<screen>
+$ dpkg -i nix_0.13pre18104-1_amd64.deb</screen>

 </para>

-<para>The RPMs install into the directory <filename>/nix</filename>.
-Nix can be uninstalled using <command>rpm -e nix</command>.  After
-this it will be necessary to manually remove the Nix store and other
-auxiliary data:
+<para>Nix can be uninstalled using <command>rpm -e nix</command> or
+<command>dpkg -r nix</command>.  After this you should manually remove
+the Nix store and other auxiliary data, if desired:

 <screen>
 $ rm -rf /nix/store
@@ -191,6 +192,7 @@ $ rm -rf /nix/var</screen>
 </section>


+<!-- TODO: should be updated
 <section><title>Upgrading Nix through Nix</title>

 <para>You can install the latest stable version of Nix through Nix
@@ -203,6 +205,7 @@ installation</link> by clicking on the package links at <link
 xlink:href="http://nixos.org/releases/full-index-nix.html" />.</para>

 </section>
+-->


 <section><title>Security</title>
--- a/doc/manual/introduction.xml
+++ b/doc/manual/introduction.xml
@@ -320,7 +320,7 @@ overview of NixOS is given in the HotOS XI paper <citetitle
 xlink:href="http://www.st.ewi.tudelft.nl/~dolstra/pubs/hotos-final.pdf">Purely
 Functional System Configuration Management</citetitle>.  The Nix
 homepage has <link
-xlink:href="http://nix.cs.uu.nl/docs/papers.html">an up-to-date list
+xlink:href="http://nixos.org/docs/papers.html">an up-to-date list
 of Nix-related papers</link>.</para>

 <para>Nix is the subject of Eelco Dolstra’s PhD thesis <citetitle
--- a/doc/manual/manual.xml
+++ b/doc/manual/manual.xml
@@ -17,6 +17,7 @@
        <orgname>Delft University of Technology</orgname>
        <orgdiv>Department of Software Technology</orgdiv>
      </affiliation>
+      <contrib>Author</contrib>
    </author>

    <copyright>
@@ -25,10 +26,11 @@
      <year>2006</year>
      <year>2007</year>
      <year>2008</year>
+      <year>2009</year>
      <holder>Eelco Dolstra</holder>
    </copyright>

-    <date>November 2008</date>
+    <date>September 2009</date>
    
  </info>

@@ -49,64 +51,25 @@
    
    <section>
      <title>Main commands</title>
-      <section xml:id="sec-nix-env">
-        <title>nix-env</title>
-        <xi:include href="nix-env.xml" />
-      </section>
-      <section xml:id="sec-nix-instantiate">
-        <title>nix-instantiate</title>
-        <xi:include href="nix-instantiate.xml" />
-      </section>
-      <section xml:id="sec-nix-store">
-        <title>nix-store</title>
-        <xi:include href="nix-store.xml" />
-      </section>
+      <xi:include href="nix-env.xml" />
+      <xi:include href="nix-instantiate.xml" />
+      <xi:include href="nix-store.xml" />
    </section>
    
    <section>
      <title>Utilities</title>
-      <section xml:id="sec-nix-build">
-        <title>nix-build</title>
-        <xi:include href="nix-build.xml" />
-      </section>
-      <section xml:id="sec-nix-channel">
-        <title>nix-channel</title>
-        <xi:include href="nix-channel.xml" />
-      </section>
-      <section xml:id="sec-nix-collect-garbage">
-        <title>nix-collect-garbage</title>
-        <xi:include href="nix-collect-garbage.xml" />
-      </section>
-      <section xml:id="sec-nix-copy-closure">
-        <title>nix-copy-closure</title>
-        <xi:include href="nix-copy-closure.xml" />
-      </section>
-      <section xml:id="sec-nix-hash">
-        <title>nix-hash</title>
-        <xi:include href="nix-hash.xml" />
-      </section>
-      <section xml:id="sec-nix-install-package">
-        <title>nix-install-package</title>
-        <xi:include href="nix-install-package.xml" />
-      </section>
-      <section xml:id="sec-nix-prefetch-url">
-        <title>nix-prefetch-url</title>
-        <xi:include href="nix-prefetch-url.xml" />
-      </section>
-      <section xml:id="sec-nix-pull">
-        <title>nix-pull</title>
-        <xi:include href="nix-pull.xml" />
-      </section>
-      <section xml:id="sec-nix-push">
-        <title>nix-push</title>
-        <xi:include href="nix-push.xml" />
-      </section>
-      <section xml:id="sec-nix-worker">
-        <title>nix-worker</title>
-        <xi:include href="nix-worker.xml" />
-      </section>
+      <xi:include href="nix-build.xml" />
+      <xi:include href="nix-channel.xml" />
+      <xi:include href="nix-collect-garbage.xml" />
+      <xi:include href="nix-copy-closure.xml" />
+      <xi:include href="nix-hash.xml" />
+      <xi:include href="nix-install-package.xml" />
+      <xi:include href="nix-prefetch-url.xml" />
+      <xi:include href="nix-pull.xml" />
+      <xi:include href="nix-push.xml" />
+      <xi:include href="nix-worker.xml" />
    </section>
-    
+
  </appendix>

  <xi:include href="troubleshooting.xml" />
--- a/doc/manual/nix-build.xml
+++ b/doc/manual/nix-build.xml
@@ -1,6 +1,7 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
-          xmlns:xi="http://www.w3.org/2001/XInclude">
+          xmlns:xi="http://www.w3.org/2001/XInclude"
+          xml:id="sec-nix-build">

 <refmeta>
  <refentrytitle>nix-build</refentrytitle>
--- a/doc/manual/nix-channel.xml
+++ b/doc/manual/nix-channel.xml
@@ -1,6 +1,7 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
-          xmlns:xi="http://www.w3.org/2001/XInclude">
+          xmlns:xi="http://www.w3.org/2001/XInclude"
+          xml:id="sec-nix-channel">
  
 <refmeta>
  <refentrytitle>nix-channel</refentrytitle>
--- a/doc/manual/nix-collect-garbage.xml
+++ b/doc/manual/nix-collect-garbage.xml
@@ -1,6 +1,7 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
-          xmlns:xi="http://www.w3.org/2001/XInclude">
+          xmlns:xi="http://www.w3.org/2001/XInclude"
+          xml:id="sec-nix-collect-garbage">
  
 <refmeta>
  <refentrytitle>nix-collect-garbage</refentrytitle>
--- a/doc/manual/nix-copy-closure.xml
+++ b/doc/manual/nix-copy-closure.xml
@@ -1,6 +1,7 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
-          xmlns:xi="http://www.w3.org/2001/XInclude">
+          xmlns:xi="http://www.w3.org/2001/XInclude"
+          xml:id="sec-nix-copy-closure">

 <refmeta>
  <refentrytitle>nix-copy-closure</refentrytitle>
--- a/doc/manual/nix-env.xml
+++ b/doc/manual/nix-env.xml
@@ -1,6 +1,7 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
-          xmlns:xi="http://www.w3.org/2001/XInclude">
+          xmlns:xi="http://www.w3.org/2001/XInclude"
+          xml:id="sec-nix-env">
  
 <refmeta>
  <refentrytitle>nix-env</refentrytitle>
--- a/doc/manual/nix-hash.xml
+++ b/doc/manual/nix-hash.xml
@@ -1,6 +1,7 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
-          xmlns:xi="http://www.w3.org/2001/XInclude">
+          xmlns:xi="http://www.w3.org/2001/XInclude"
+          xml:id="sec-nix-hash">
  
 <refmeta>
  <refentrytitle>nix-hash</refentrytitle>
--- a/doc/manual/nix-install-package.xml
+++ b/doc/manual/nix-install-package.xml
@@ -1,6 +1,7 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
-          xmlns:xi="http://www.w3.org/2001/XInclude">
+          xmlns:xi="http://www.w3.org/2001/XInclude"
+          xml:id="sec-nix-install-package">
  
 <refmeta>
  <refentrytitle>nix-install-package</refentrytitle>
--- a/doc/manual/nix-instantiate.xml
+++ b/doc/manual/nix-instantiate.xml
@@ -1,6 +1,7 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
-          xmlns:xi="http://www.w3.org/2001/XInclude">
+          xmlns:xi="http://www.w3.org/2001/XInclude"
+          xml:id="sec-nix-instantiate">
  
 <refmeta>
  <refentrytitle>nix-instantiate</refentrytitle>
--- a/doc/manual/nix-lang-ref.xml
+++ b/doc/manual/nix-lang-ref.xml
@@ -178,100 +178,5 @@
    </productionset>
    
  </sect1>
-  
-
-
-  <sect1>
-    <title>Semantics</title>
-
-
-    
-    <sect2>
-      <title>Built-in functions</title>
-
-      <para>
-        The Nix language provides the following built-in function
-        (<quote>primops</quote>):
-      </para>
-
-      <variablelist>
-
-        <varlistentry>
-          <term><function>import</function>
-          <replaceable>e</replaceable></term>
-          <listitem>
-            <para>
-              Evaluates the expression <replaceable>e</replaceable>,
-              which must yield a path value.  The Nix expression
-              stored at this path in the file system is then read,
-              parsed, and evaluated.  Returns the result of the
-              evaluation of the Nix expression just read.
-            </para>
-
-            <para>
-              Example: <literal>import ./foo.nix</literal> evaluates
-              the expression stored in <filename>foo.nix</filename>
-              (in the directory containing the expression in which the
-              <function>import</function> occurs).
-            </para>
-          </listitem>
-        </varlistentry>
-
-        <varlistentry>
-          <term><function>derivation</function>
-          <replaceable>e</replaceable></term>
-          <listitem>
-            <para>
-              Evaluates the expression <replaceable>e</replaceable>,
-              which must yield an attribute set.  [...]
-            </para>
-          </listitem>
-        </varlistentry>
-
-        <varlistentry>
-          <term><function>baseNameOf</function>
-          <replaceable>e</replaceable></term>
-          <listitem>
-            <para>
-              Evaluates the expression <replaceable>e</replaceable>,
-              which must yield a string value, and returns a string
-              representing its <emphasis>base name</emphasis>.  This
-              is the substring following the last path separator
-              (<literal>/</literal>).
-            </para>
-
-            <para>
-              Example: <literal>baseNameOf "/foo/bar"</literal>
-              returns <literal>"bar"</literal>, and
-              <literal>baseNameOf "/foo/bar/"</literal> returns
-              <literal>""</literal>.
-            </para>
-          </listitem>
-        </varlistentry>
-
-        <varlistentry>
-          <term><function>toString</function>
-          <replaceable>e</replaceable></term>
-          <listitem>
-            <para>
-              Evaluates the expression <replaceable>e</replaceable>
-              and coerces it into a string, if possible.  Only
-              strings, paths, and URIs can be so coerced.
-            </para>
-
-            <para>
-              Example: <literal>toString
-              http://www.cs.uu.nl/</literal> returns
-              <literal>"http://www.cs.uu.nl/"</literal>.
-            </para>
-          </listitem>
-        </varlistentry>
-            
-      </variablelist>
-
-    </sect2>
-
-  </sect1>
-  

 </appendix>
--- a/doc/manual/nix-prefetch-url.xml
+++ b/doc/manual/nix-prefetch-url.xml
@@ -1,6 +1,7 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
-          xmlns:xi="http://www.w3.org/2001/XInclude">
+          xmlns:xi="http://www.w3.org/2001/XInclude"
+          xml:id="sec-nix-prefetch-url">
  
 <refmeta>
  <refentrytitle>nix-prefetch-url</refentrytitle>
--- a/doc/manual/nix-pull.xml
+++ b/doc/manual/nix-pull.xml
@@ -1,6 +1,7 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
-          xmlns:xi="http://www.w3.org/2001/XInclude">
+          xmlns:xi="http://www.w3.org/2001/XInclude"
+          xml:id="sec-nix-pull">

 <refmeta>
  <refentrytitle>nix-pull</refentrytitle>
--- a/doc/manual/nix-push.xml
+++ b/doc/manual/nix-push.xml
@@ -1,6 +1,7 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
-          xmlns:xi="http://www.w3.org/2001/XInclude">
+          xmlns:xi="http://www.w3.org/2001/XInclude"
+          xml:id="sec-nix-push">

 <refmeta>
  <refentrytitle>nix-push</refentrytitle>
--- a/doc/manual/nix-store.xml
+++ b/doc/manual/nix-store.xml
@@ -1,6 +1,7 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
-          xmlns:xi="http://www.w3.org/2001/XInclude">
+          xmlns:xi="http://www.w3.org/2001/XInclude"
+          xml:id="sec-nix-store">

 <refmeta>
  <refentrytitle>nix-store</refentrytitle>
@@ -212,8 +213,6 @@ linkend="sec-nix-build"><command>nix-build</command></link> does.</para>
  </group>
  <arg><option>--max-freed</option> <replaceable>bytes</replaceable></arg>
  <arg><option>--max-links</option> <replaceable>nrlinks</replaceable></arg>
-  <arg><option>--max-atime</option> <replaceable>atime</replaceable></arg>
-  <arg><option>--use-atime</option></arg>
 </cmdsynopsis>

 </refsection>
@@ -291,42 +290,6 @@ options control what gets deleted and in what order:
    
  </varlistentry>

-  <varlistentry><term><option>--max-atime</option> <replaceable>atime</replaceable></term>
-  
-    <listitem><para>Only delete a store path if its last-accessed time
-    is less than <replaceable>atime</replaceable>.  This allows you to
-    garbage-collect only packages that haven’t been used recently.
-    The time is expressed as the number of seconds in the Unix epoch,
-    i.e., since 1970-01-01 00:00:00 UTC.  An easy way to convert to
-    this format is <literal>date +%s -d "<replaceable>date
-    specification</replaceable>"</literal>.</para>
-
-    <para>For directories, the last-accessed time is the highest
-    last-accessed time of any regular file in the directory (or in any
-    of its subdirectories).  That is, the <literal>atime</literal>
-    field maintained by the filesystem is ignored for directories.
-    This is because operations such as rebuilding the
-    <command>locate</command> database tend to update the
-    <literal>atime</literal> values of all directories, so they’re not
-    a useful indicator of whether a package was recently used.</para>
-
-    <para>Note that <command>nix-store --optimise</command> reads all
-    regular files in the Nix store, and so causes all last-accessed
-    times to be set to the present time.  This makes
-    <option>--max-atime</option> ineffective (for a while at
-    least).</para></listitem>
-    
-  </varlistentry>
-
-  <varlistentry><term><option>--use-atime</option></term>
-
-    <listitem><para>Delete store paths in order of ascending
-    last-accessed time.  This is useful in conjunction with the other
-    options to delete only the least recently used
-    packages.</para></listitem>
-
-  </varlistentry>
-  
 </variablelist>

 </para>
@@ -357,13 +320,6 @@ deleting `/nix/store/kq82idx6g0nyzsp2s14gfsc38npai7lf-cairo-1.0.4.tar.gz.drv'

 </para>

-<para>To delete unreachable paths not accessed in the last two months:
-
-<screen>
-$ nix-store --gc -v --max-atime $(date +%s -d "2 months ago")</screen>
-
-</para>
-
 <para>To delete at least 100 MiBs of unreachable paths:

 <screen>
@@ -448,6 +404,7 @@ error: cannot delete path `/nix/store/zq0h41l75vlb4z45kzgjjmsjxvcv1qk7-mesa-6.4'
    <arg choice='plain'><option>--tree</option></arg>
    <arg choice='plain'><option>--binding</option> <replaceable>name</replaceable></arg>
    <arg choice='plain'><option>--hash</option></arg>
+    <arg choice='plain'><option>--roots</option></arg>
  </group>
  <arg><option>--use-output</option></arg>
  <arg><option>-u</option></arg>
@@ -630,12 +587,20 @@ query is applied to the target of the symlink.</para>
  <varlistentry><term><option>--hash</option></term>
  
    <listitem><para>Prints the SHA-256 hash of the contents of the
-    store path <replaceable>paths</replaceable>.  Since the hash is
+    store paths <replaceable>paths</replaceable>.  Since the hash is
    stored in the Nix database, this is a fast
    operation.</para></listitem>

  </varlistentry>

+  <varlistentry><term><option>--roots</option></term>
+  
+    <listitem><para>Prints the garbage collector roots that point,
+    directly or indirectly, at the store paths
+    <replaceable>paths</replaceable>.</para></listitem>
+
+  </varlistentry>
+
 </variablelist>

 </refsection>
@@ -713,6 +678,18 @@ $ gv graph.ps</screen>

 </para>

+<para>Show every garbage collector root that points to a store path
+that depends on <command>svn</command>:
+
+<screen>
+$ nix-store -q --roots $(which svn)
+/nix/var/nix/profiles/default-81-link
+/nix/var/nix/profiles/default-82-link
+/nix/var/nix/profiles/per-user/eelco/profile-97-link
+</screen>
+
+</para>
+
 </refsection>


--- a/doc/manual/nix-worker.xml
+++ b/doc/manual/nix-worker.xml
@@ -1,6 +1,7 @@
 <refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
-          xmlns:xi="http://www.w3.org/2001/XInclude">
+          xmlns:xi="http://www.w3.org/2001/XInclude"
+          xml:id="sec-nix-worker">

 <refmeta>
  <refentrytitle>nix-worker</refentrytitle>
--- a/doc/manual/package-management.xml
+++ b/doc/manual/package-management.xml
@@ -331,7 +331,7 @@ default profile, respectively.  If the profile doesn’t exist, it will
 be created automatically.  You should be careful about storing a
 profile in another location than the <filename>profiles</filename>
 directory, since otherwise it might not be used as a root of the
-garbage collector (see section <xref linkend='sec-garbage-collection'
+garbage collector (see <xref linkend='sec-garbage-collection'
 />).</para>

 <para>All <command>nix-env</command> operations work on the profile
@@ -507,19 +507,16 @@ click on it, and it will be installed with all the necessary
 dependencies.</para>

 <para>For instance, you can go to <link
-xlink:href="http://nixos.org/releases/nixpkgs/nixpkgs-unstable/" /> —
-or to any older release of Nix Packages — and click on any link for
-the individual packages for your platform (say, <link
-xlink:href='http://nix.cs.uu.nl/dist/nix/nixpkgs-0.10pre6622/pkgs/subversion-1.4.0-i686-linux.nixpkg'><literal>subversion-1.4.0</literal>
-for <literal>i686-linux</literal></link>).  The first time you do
-this, your browser will ask what to do with
-<literal>application/nix-package</literal> files.  You should open
-them with <filename>/nix/bin/nix-install-package</filename>.  This
-will open a window that asks you to confirm that you want to install
-the package.  When you answer <literal>Y</literal>, the package and
-all its dependencies will be installed.  This is a binary deployment
-mechanism — you get packages pre-compiled for the selected platform
-type.</para>
+xlink:href="http://hydra.nixos.org/jobset/nixpkgs/trunk/channel/latest"
+/> and click on any link for the individual packages for your
+platform.  The first time you do this, your browser will ask what to
+do with <literal>application/nix-package</literal> files.  You should
+open them with <filename>/nix/bin/nix-install-package</filename>.
+This will open a window that asks you to confirm that you want to
+install the package.  When you answer <literal>Y</literal>, the
+package and all its dependencies will be installed.  This is a binary
+deployment mechanism — you get packages pre-compiled for the selected
+platform type.</para>

 <para>You can also install <literal>application/nix-package</literal>
 files from the command line directly.  See <xref
--- a/doc/manual/quick-start.xml
+++ b/doc/manual/quick-start.xml
@@ -1,5 +1,6 @@
 <chapter xmlns="http://docbook.org/ns/docbook"
-         xmlns:xlink="http://www.w3.org/1999/xlink">
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xml:id="chap-quick-start">

 <title>Quick Start</title>

@@ -10,9 +11,9 @@ to the following chapters.</para>

 <orderedlist>

-<listitem><para>Download a source tarball or RPM from <link
-xlink:href='http://nixos.org/'/>.  Build source
-distributions using the regular sequence:
+<listitem><para>Download a source tarball, RPM or Deb from <link
+xlink:href='http://nixos.org/'/>.  Build source distributions using
+the regular sequence:
        
 <screen>
 $ tar xvfj nix-<replaceable>version</replaceable>.tar.bz2
@@ -20,13 +21,21 @@ $ ./configure
 $ make
 $ make install <lineannotation>(as root)</lineannotation></screen>

-This will install Nix in <filename>/nix</filename>.  You shouldn't
-change the prefix if at all possible since that will make it
-impossible to use pre-built binaries from the Nixpkgs channel and
-other channels.  Alternatively, you could grab an RPM if you're on an
-RPM-based system.  You should also add
-<filename>/nix/etc/profile.d/nix.sh</filename> to your
-<filename>~/.bashrc</filename> (or some other login
+This will install the Nix binaries in <filename>/usr/local</filename>
+and keep the Nix store and other state in <filename>/nix</filename>.
+You can change the former by specifying
+<option>--prefix=<replaceable>path</replaceable></option>.  The
+location of the store can be changed using
+<option>--with-store-dir=<replaceable>path</replaceable></option>.
+However, you shouldn't change the store location, if at all possible,
+since that will make it impossible to use pre-built binaries from the
+Nixpkgs channel and other channels.  The location of the state can be
+changed using
+<option>--localstatedir=<replaceable>path</replaceable>.</option></para></listitem>
+
+<listitem><para>You should add
+<filename><replaceable>prefix</replaceable>/etc/profile.d/nix.sh</filename>
+to your <filename>~/.bashrc</filename> (or some other login
 file).</para></listitem>

 <listitem><para>Subscribe to the Nix Packages channel.
@@ -99,7 +108,7 @@ numbers).</para></listitem>

 <listitem><para>You can also install specific packages directly from
 your web browser.  For instance, you can go to <link
-xlink:href="http://nix.cs.uu.nl/dist/nix/nixpkgs-unstable-latest/" />
+xlink:href="http://hydra.nixos.org/jobset/nixpkgs/trunk/channel/latest" />
 and click on any link for the individual packages for your platform.
 Associate <literal>application/nix-package</literal> with the program
 <filename>/nix/bin/nix-install-package</filename>.  A window should
--- a/doc/manual/release-notes.xml
+++ b/doc/manual/release-notes.xml
@@ -8,7 +8,47 @@

 <!--==================================================================-->

-<section xml:id="ssec-relnotes-0.13"><title>Release 0.13 (April NN,
+<section xml:id="ssec-relnotes-0.14"><title>Release 0.14 (TBA)</title>
+
+<para>This release has the following improvements:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>The garbage collector now starts deleting garbage much
+    faster than before.  It no longer determines liveness of all paths
+    in the store, but does so on demand.</para>
+  </listitem>
+
+  <listitem>
+    <para>Added a new operation, <command>nix-store --query
+    --roots</command>, that shows the garbage collector roots that
+    directly or indirectly point to the given store paths.</para>
+  </listitem>
+
+  <listitem>
+    <para>Removed support for converting Berkeley DB-based Nix
+    databases to the new schema.</para>
+  </listitem>
+
+  <listitem>
+    <para>Removed the <option>--use-atime</option> and
+    <option>--max-atime</option> garbage collector options.  They were
+    not very useful in practice.</para>
+  </listitem>
+
+  <listitem>
+    <para>A few bug fixes.</para>
+  </listitem>
+
+</itemizedlist>
+
+</section>
+
+
+<!--==================================================================-->
+
+<section xml:id="ssec-relnotes-0.13"><title>Release 0.13 (November 5,
 2009)</title>

 <para>This is primarily a bug fix release.  It has some new
@@ -85,7 +125,25 @@ features:</para>
    add a string to stack traces — useful for debugging),
    <varname>builtins.isBool</varname>,
    <varname>builtins.isString</varname>,
-    <varname>builtins.isInt</varname>.</para>
+    <varname>builtins.isInt</varname>,
+    <varname>builtins.intersectAttrs</varname>.</para>
+  </listitem>
+
+  <listitem>
+    <para>OpenSolaris support (Sander van der Burg).</para>
+  </listitem>
+
+  <listitem>
+    <para>Stack traces are no longer displayed unless the
+    <option>--show-trace</option> option is used.</para>
+  </listitem>
+
+  <listitem>
+    <para>The scoping rules for <literal>inherit
+    (<replaceable>e</replaceable>) ...</literal> in recursive
+    attribute sets have changed.  The expression
+    <replaceable>e</replaceable> can now refer to the attributes
+    defined in the containing set.</para>
  </listitem>

 </itemizedlist>
--- a/doc/manual/writing-nix-expressions.xml
+++ b/doc/manual/writing-nix-expressions.xml
@@ -1106,7 +1106,7 @@ used in the Nix expression for Subversion.</para>
    incompatibility might occur.</para>
  </callout>

-  <callout arearefs='ex-subversion-nix-co-2'>
+  <callout arearefs='ex-subversion-nix-co-3'>
    <para>This assertion says that in order for Subversion to have SSL
    support (so that it can access <literal>https</literal> URLs), an
    OpenSSL library must be passed.  Additionally, it says that
--- a/externals/Makefile.am
+++ b/externals/Makefile.am
@@ -1,46 +1,3 @@
-# Berkeley DB
-
-DB = db-4.5.20
-
-if OLD_DB_COMPAT
-
-$(DB).tar.gz:
-	@echo "Nix requires Berkeley DB to build."
-	@echo "Please download version 4.5.20 from"
-	@echo "  http://download-east.oracle.com/berkeley-db/db-4.5.20.tar.gz"
-	@echo "and place it in the externals/ directory."
-	false
-
-$(DB): $(DB).tar.gz
-	gunzip < $(srcdir)/$(DB).tar.gz | tar xvf -
-	(cd $(DB) && $(patch) -p1) < $(srcdir)/bdb-cygwin.patch
-
-have-db:
-	$(MAKE) $(DB)
-	touch have-db
-
-if HAVE_BDB
-build-db:
-else
-build-db: have-db
-	(pfx=`pwd` && \
-	cd $(DB)/build_unix && \
-	CC="$(CC)" CXX="$(CXX)" CFLAGS="$(CFLAGS)" CXXFLAGS="$(CXXFLAGS)" \
-	 ../dist/configure --prefix=$$pfx/inst-bdb \
-	 --enable-cxx --disable-shared --disable-cryptography \
-         --disable-replication --disable-verify && \
-	$(MAKE) && \
-	$(MAKE) install_include install_lib)
-	touch build-db
-endif
-
-else
-
-build-db:
-
-endif
-
-
 # CWI ATerm

 ATERM = aterm-2.4.2-fixes-r2
@@ -107,11 +64,10 @@ install:
 endif


-all: build-db build-aterm build-bzip2
+all: build-aterm build-bzip2

-EXTRA_DIST = $(DB).tar.gz $(ATERM).tar.bz2 $(BZIP2).tar.gz \
-  bdb-cygwin.patch
+EXTRA_DIST = $(ATERM).tar.bz2 $(BZIP2).tar.gz

 ext-clean:
-	$(RM) -f have-db build-db have-aterm build-aterm have-bzip2 build-bzip2
-	$(RM) -rf $(DB) $(ATERM) $(BZIP2)
+	$(RM) -f have-aterm build-aterm have-bzip2 build-bzip2
+	$(RM) -rf $(ATERM) $(BZIP2)
--- a/externals/bdb-cygwin.patch
+++ b/externals/bdb-cygwin.patch
@@ -1,22 +0,0 @@
-diff -rc db-4.5.20-orig/os/os_flock.c db-4.5.20/os/os_flock.c
-*** db-4.5.20-orig/os/os_flock.c	2006-10-13 12:36:12.000000000 +0200
--- db-4.5.20/os/os_flock.c	2006-10-13 12:40:11.000000000 +0200
-***************
-*** 30,35 ****
--- 30,44 ----
-  
-  	DB_ASSERT(dbenv, F_ISSET(fhp, DB_FH_OPENED) && fhp->fd != -1);
-  
-+ #ifdef __CYGWIN__
-+ 	/*
-+ 	 * Windows file locking interferes with read/write operations, so we
-+ 	 * map the ranges to an area past the end of the file.
-+ 	 */
-+ 	DB_ASSERT(dbenv, offset < (off_t) 1 << 62);
-+ 	offset += (off_t) 1 << 62;
-+ #endif
-+ 
-  	fl.l_start = offset;
-  	fl.l_len = 1;
-  	fl.l_type = acquire ? F_WRLCK : F_UNLCK;
-Only in db-4.5.20/os: os_flock.c~
--- a/release.nix
+++ b/release.nix
@@ -18,7 +18,10 @@ let
        src = nix;
        inherit officialRelease;

-        buildInputs = [curl bison flex2533 perl libxml2 libxslt w3m bzip2 jing_tools tetex dblatex];
+        buildInputs =
+          [ curl bison flex2533 perl libxml2 libxslt w3m bzip2
+            tetex dblatex nukeReferences
+          ];

        configureFlags = ''
          --with-docbook-rng=${docbook5}/xml/rng/docbook
@@ -26,27 +29,16 @@ let
          --with-xml-flags=--nonet
        '';

-        # Include the BDB, ATerm and Bzip2 tarballs in the distribution.
+        # Include the ATerm and Bzip2 tarballs in the distribution.
        preConfigure = ''
-          stripHash ${db45.src}
-          # Remove unnecessary stuff from the Berkeley DB tarball.
-          ( mkdir bdb-temp
-            cd bdb-temp
-            tar xfz ${db45.src}
-            cd *
-            rm -rf docs test tcl perl libdb_java java rpc_server build_vxworks \
-              examples_java examples_c examples_cxx dist/tags
-            mkdir test
-            touch test/include.tcl
-            cd ..
-            tar cvfz ../externals/$strippedName *
-          )
-
          stripHash ${aterm242fixes.src}
          cp -pv ${aterm242fixes.src} externals/$strippedName

          stripHash ${bzip2.src}
          cp -pv ${bzip2.src} externals/$strippedName
+
+          # TeX needs a writable font cache.
+          export VARTEXFONTS=$TMPDIR/texfonts
        '';

        preDist = ''
@@ -54,6 +46,14 @@ let
          
          make -C doc/manual manual.pdf prefix=$out
          cp doc/manual/manual.pdf $out/manual.pdf
+
+          # The PDF containes filenames of included graphics (see
+          # http://www.tug.org/pipermail/pdftex/2007-August/007290.html).
+          # This causes a retained dependency on dblatex, which Hydra
+          # doesn't like (the output of the tarball job is distributed
+          # to Windows and Macs, so there should be no Linux binaries
+          # in the closure).
+          nuke-refs $out/manual.pdf
          
          echo "doc manual $out/share/doc/nix/manual" >> $out/nix-support/hydra-build-products
          echo "doc-pdf manual $out/manual.pdf" >> $out/nix-support/hydra-build-products
@@ -77,11 +77,12 @@ let

        configureFlags = ''
          --disable-init-state
-          --with-bdb=${db45} --with-aterm=${aterm242fixes} --with-bzip2=${bzip2}
+          --with-aterm=${aterm242fixes} --with-bzip2=${bzip2}
        '';
      };

-      
+
+    /*
    static =
      { tarball ? jobs.tarball {}
      , system ? "i686-linux"
@@ -97,10 +98,11 @@ let

        configureFlags = ''
          --disable-init-state
-          --disable-old-db-compat --with-aterm=${aterm242fixes} --with-bzip2=${bzip2}
+          --with-aterm=${aterm242fixes} --with-bzip2=${bzip2}
          --enable-static-nix
        '';
      };
+    */

      
    coverage =
@@ -121,7 +123,7 @@ let

        configureFlags = ''
          --disable-init-state --disable-shared
-          --with-bdb=${db45} --with-aterm=${aterm242fixes} --with-bzip2=${bzip2}
+          --with-aterm=${aterm242fixes} --with-bzip2=${bzip2}
        '';

        lcovFilter = ["*/boost/*" "*-tab.*"];
@@ -133,22 +135,32 @@ let
      };

      
-    rpm_fedora5i386 = makeRPM_i686 (diskImages: diskImages.fedora5i386) 20;
-    rpm_fedora9i386 = makeRPM_i686 (diskImages: diskImages.fedora9i386) 50;
-    rpm_fedora9x86_64 = makeRPM_x86_64 (diskImages: diskImages.fedora9x86_64) 50;
-    rpm_fedora10i386 = makeRPM_i686 (diskImages: diskImages.fedora10i386) 40;
-    rpm_fedora10x86_64 = makeRPM_x86_64 (diskImages: diskImages.fedora10x86_64) 40;
+    rpm_fedora5i386 = makeRPM_i686 (diskImages: diskImages.fedora5i386) 10;
+    rpm_fedora9i386 = makeRPM_i686 (diskImages: diskImages.fedora9i386) 20;
+    rpm_fedora9x86_64 = makeRPM_x86_64 (diskImages: diskImages.fedora9x86_64) 20;
+    rpm_fedora10i386 = makeRPM_i686 (diskImages: diskImages.fedora10i386) 30;
+    rpm_fedora10x86_64 = makeRPM_x86_64 (diskImages: diskImages.fedora10x86_64) 30;
+    rpm_fedora11i386 = makeRPM_i686 (diskImages: diskImages.fedora11i386) 40;
+    rpm_fedora11x86_64 = makeRPM_x86_64 (diskImages: diskImages.fedora11x86_64) 40;
+    rpm_fedora12i386 = makeRPM_i686 (diskImages: diskImages.fedora12i386) 50;
+    rpm_fedora12x86_64 = makeRPM_x86_64 (diskImages: diskImages.fedora12x86_64) 50;
    rpm_opensuse103i386 = makeRPM_i686 (diskImages: diskImages.opensuse103i386) 40;
+    rpm_opensuse110i386 = makeRPM_i686 (diskImages: diskImages.opensuse110i386) 50;
+    rpm_opensuse110x86_64 = makeRPM_x86_64 (diskImages: diskImages.opensuse110x86_64) 50;

    
    deb_debian40i386 = makeDeb_i686 (diskImages: diskImages.debian40i386) 40;
    deb_debian40x86_64 = makeDeb_x86_64 (diskImages: diskImages.debian40x86_64) 40;
-    deb_debian50i386 = makeDeb_i686 (diskImages: diskImages.debian50i386) 30;
-    deb_debian50x86_64 = makeDeb_x86_64 (diskImages: diskImages.debian50x86_64) 30;
-    deb_ubuntu804i386 = makeDeb_i686 (diskImages: diskImages.ubuntu804i386) 50;
-    deb_ubuntu804x86_64 = makeDeb_x86_64 (diskImages: diskImages.ubuntu804x86_64) 50;
-    deb_ubuntu810i386 = makeDeb_i686 (diskImages: diskImages.ubuntu810i386) 40;
-    deb_ubuntu810x86_64 = makeDeb_x86_64 (diskImages: diskImages.ubuntu810x86_64) 40;
+    deb_debian50i386 = makeDeb_i686 (diskImages: diskImages.debian50i386) 50;
+    deb_debian50x86_64 = makeDeb_x86_64 (diskImages: diskImages.debian50x86_64) 50;
+    deb_ubuntu804i386 = makeDeb_i686 (diskImages: diskImages.ubuntu804i386) 20;
+    deb_ubuntu804x86_64 = makeDeb_x86_64 (diskImages: diskImages.ubuntu804x86_64) 20;
+    deb_ubuntu810i386 = makeDeb_i686 (diskImages: diskImages.ubuntu810i386) 30;
+    deb_ubuntu810x86_64 = makeDeb_x86_64 (diskImages: diskImages.ubuntu810x86_64) 30;
+    deb_ubuntu904i386 = makeDeb_i686 (diskImages: diskImages.ubuntu904i386) 40;
+    deb_ubuntu904x86_64 = makeDeb_x86_64 (diskImages: diskImages.ubuntu904x86_64) 40;
+    deb_ubuntu910i386 = makeDeb_i686 (diskImages: diskImages.ubuntu910i386) 50;
+    deb_ubuntu910x86_64 = makeDeb_x86_64 (diskImages: diskImages.ubuntu910x86_64) 50;


  };
@@ -190,6 +202,7 @@ let
      memSize = 1024;
      meta = { schedulingPriority = toString prio; };
      configureFlags = "--sysconfdir=/etc";
+      debRequires = ["curl"];
    };


--- a/scripts/build-remote.pl.in
+++ b/scripts/build-remote.pl.in
@@ -47,24 +47,21 @@ decline if !defined $conf || ! -e $conf;
 my $canBuildLocally = $amWilling && ($localSystem eq $neededSystem);


-# Otherwise find a willing remote machine.
-my @machines;
-my %curJobs;
-
-
 # Read the list of machines.
+my @machines;
 open CONF, "< $conf" or die;

 while (<CONF>) {
    chomp;
    s/\#.*$//g;
    next if /^\s*$/;
-    /^\s*(\S+)\s+(\S+)\s+(\S+)\s+(\d+)\s*$/ or die;
+    /^\s*(\S+)\s+(\S+)\s+(\S+)\s+(\d+)(\s+([0-9\.]+))?\s*$/ or die;
    push @machines,
        { hostName => $1
-        , systemType => $2
+        , systemTypes => [split(/,/, $2)]
        , sshKeys => $3
        , maxJobs => $4
+        , speedFactor => 1.0 * ($6 || 1)
        };
 }

@@ -77,39 +74,53 @@ open MAINLOCK, ">>$mainLock" or die;
 flock(MAINLOCK, LOCK_EX) or die;


-# Find a suitable system.
+sub openSlotLock {
+    my ($machine, $slot) = @_;
+    my $slotLockFn = "$currentLoad/" . (join '+', @{$machine->{systemTypes}}) . "-" . $machine->{hostName} . "-$slot";
+    my $slotLock = new IO::Handle;
+    open $slotLock, ">>$slotLockFn" or die;
+    return $slotLock;
+}
+    
+
+# Find all machine that can execute this build, i.e., that support
+# builds for the given platform and are not at their job limit.
 my $rightType = 0;
-my $machine;
-my $slotLock;
+my @available = ();
 LOOP: foreach my $cur (@machines) {
-    if ($neededSystem eq $cur->{systemType}
-        || ($neededSystem eq "i686-linux" && $cur->{systemType} eq "x86_64-linux"))
-    {
+    if (grep { $neededSystem eq $_ } @{$cur->{systemTypes}}) {
        $rightType = 1;

-        # We have a machine of the right type.  Try to get a lock on
-        # one of the machine's lock files.
+        # We have a machine of the right type.  Determine the load on
+        # the machine.
        my $slot = 0;
+        my $load = 0;
+        my $free;
        while ($slot < $cur->{maxJobs}) {
-            my $slotLockFn = "$currentLoad/" . $cur->{systemType} . "-" . $cur->{hostName} . "-$slot";
-            $slotLock = new IO::Handle;
-            open $slotLock, ">>$slotLockFn" or die;
+            my $slotLock = openSlotLock($cur, $slot);
            if (flock($slotLock, LOCK_EX | LOCK_NB)) {
-                utime undef, undef, $slotLock;
-                $machine = $cur;
-                last LOOP;
+                $free = $slot unless defined $free;
+                flock($slotLock, LOCK_UN) or die;
+            } else {
+                $load++;
            }
            close $slotLock;
            $slot++;
        }
+
+        push @available, { machine => $cur, load => $load, free => $free }
+            if $load < $cur->{maxJobs};
    }
 }

-close MAINLOCK;
+if (defined $ENV{NIX_DEBUG_HOOK}) {
+    print STDERR "load on " . $_->{machine}->{hostName} . " = " . $_->{load} . "\n"
+        foreach @available;
+}


-# Didn't find one?  Then decline or postpone.
-if (!defined $machine) {
+# Didn't find any available machine?  Then decline or postpone.
+if (scalar @available == 0) {
    # Postpone if we have a machine of the right type, except if the
    # local system can and wants to do the build.
    if ($rightType && !$canBuildLocally) {
@@ -120,8 +131,41 @@ if (!defined $machine) {
    }
 }

-# Yes we did, accept.
+
+# Prioritise the available machines as follows:
+# - First by load divided by speed factor, rounded to the nearest
+#   integer.  This causes fast machines to be preferred over slow
+#   machines with similar loads.
+# - Then by speed factor.
+# - Finally by load.
+sub lf { my $x = shift; return int($x->{load} / $x->{machine}->{speedFactor} + 0.4999); }
+@available = sort
+    { lf($a) <=> lf($b)
+          || $b->{machine}->{speedFactor} <=> $a->{machine}->{speedFactor}
+          || $a->{load} <=> $b->{load}
+    } @available;
+
+
+# Select the best available machine and lock a free slot.
+my $selected = $available[0]; 
+my $machine = $selected->{machine};
+
+my $slotLock = openSlotLock($machine, $selected->{free});
+flock($slotLock, LOCK_EX | LOCK_NB) or die;
+utime undef, undef, $slotLock;
+
+close MAINLOCK;
+
+
+# Tell Nix we've accepted the build.
 sendReply "accept";
+if (defined $ENV{NIX_DEBUG_HOOK}) {
+    my $hostName = $machine->{hostName};
+    my $sp = $machine->{speedFactor};
+    print STDERR "building `$drvPath' on `$hostName' - $sp - " . $selected->{free} . "\n";
+    sleep 10;
+    exit 0;
+}
 my $x = <STDIN>;
 chomp $x;

@@ -130,7 +174,7 @@ if ($x ne "okay") {
 }


-# Do the actual job.
+# Do the actual build.
 my $hostName = $machine->{hostName};
 print STDERR "building `$drvPath' on `$hostName'\n";

@@ -178,7 +222,7 @@ print "copying inputs...\n";
 my $maybeSign = "";
 $maybeSign = "--sign" if -e "/nix/etc/nix/signing-key.sec";

-system("NIX_SSHOPTS=\"$sshOpts\" @bindir@/nix-copy-closure --gzip $hostName $maybeSign $drvPath $inputs") == 0
+system("NIX_SSHOPTS=\"$sshOpts\" @bindir@/nix-copy-closure $hostName $maybeSign $drvPath $inputs") == 0
    or die "cannot copy inputs to $hostName: $?";

 print "building...\n";
@@ -190,7 +234,7 @@ my $buildFlags = "--max-silent-time $maxSilentTime";
 # connection dies.  Without it, the remote process might continue to
 # run indefinitely (that is, until it next tries to write to
 # stdout/stderr).
-if (system("ssh -tt $sshOpts $hostName 'nix-store --realise -K $buildFlags $drvPath > /dev/null'") != 0) {
+if (system("ssh -tt $sshOpts $hostName 'nix-store --realise $buildFlags $drvPath > /dev/null'") != 0) {
    # If we couldn't run ssh or there was an ssh problem (indicated by
    # exit code 255), then we return exit code 1; otherwise we assume
    # that the builder failed, which we indicated to Nix using exit
@@ -207,6 +251,6 @@ foreach my $output (split '\n', $outputs) {
    my $maybeSignRemote = "";
    $maybeSignRemote = "--sign" if $UID != 0;
    
-    system("ssh $sshOpts $hostName 'nix-store --export $maybeSignRemote $output | gzip' | gunzip | @bindir@/nix-store --import > /dev/null") == 0
+    system("ssh $sshOpts $hostName 'nix-store --export $maybeSignRemote $output' | @bindir@/nix-store --import > /dev/null") == 0
 	or die "cannot copy $output from $hostName: $?";
 }
--- a/scripts/nix-build.in
+++ b/scripts/nix-build.in
@@ -12,6 +12,7 @@ my $outLink;
 my $drvLink;

 my $dryRun = 0;
+my $verbose = 0;

 my @instArgs = ();
 my @buildArgs = ();
@@ -112,6 +113,16 @@ EOF
        $dryRun = 1;
    }
    
+    elsif ($arg eq "--show-trace") {
+        push @instArgs, $arg;
+    }
+    
+    elsif ($arg eq "--verbose" or substr($arg, 0, 2) eq "-v") {
+        push @buildArgs, $arg;
+        push @instArgs, $arg;
+        $verbose = 1;
+    }
+    
    elsif (substr($arg, 0, 1) eq "-") {
        push @buildArgs, $arg;
    }
@@ -149,7 +160,7 @@ foreach my $expr (@exprs) {

    foreach my $drvPath (@drvPaths) {
        my $target = readlink $drvPath or die "cannot read symlink `$drvPath'";
-        print STDERR "store derivation is $target\n";
+        print STDERR "derivation is $target\n" if $verbose;
    }

    # Build.
--- a/scripts/nix-channel.in
+++ b/scripts/nix-channel.in
@@ -78,6 +78,9 @@ sub removeChannel {
 sub update {
    readChannels;

+    # Create the manifests directory if it doesn't exist.
+    mkdir "$stateDir/manifests", 0755 unless -e "$stateDir/manifests";
+
    # Do we have write permission to the manifests directory?  If not,
    # then just skip pulling the manifest and just download the Nix
    # expressions.  If the user is a non-privileged user in a
@@ -85,11 +88,6 @@ sub update {
    # source.
    if (-W "$stateDir/manifests") {

-        # Remove all the old manifests.
-        for my $manifest (glob "$stateDir/manifests/*.nixmanifest") {
-            unlink $manifest or die "cannot remove `$manifest': $!";
-        }
-
        # Pull cache manifests.
        foreach my $url (@channels) {
            #print "pulling cache manifest from `$url'\n";
--- a/scripts/nix-pull.in
+++ b/scripts/nix-pull.in
@@ -18,6 +18,12 @@ my $manifestDir = ($ENV{"NIX_MANIFESTS_DIR"} or "$stateDir/manifests");
 umask 0022;


+# Create the manifests directory if it doesn't exist.
+if (! -e $manifestDir) {
+    mkdir $manifestDir, 0755 or die "cannot create directory `$manifestDir'";
+}
+
+
 # Process the URLs specified on the command line.
 my %narFiles;
 my %localPaths;
@@ -45,7 +51,7 @@ sub processURL {

    # First see if a bzipped manifest is available.
    if (system("@curl@ --fail --silent --head '$url'.bz2 > /dev/null") == 0) {
-        print "obtaining list of Nix archives at `$url.bz2'...\n";
+        print "fetching list of Nix archives at `$url.bz2'...\n";
        my $bzipped = downloadFile "$url.bz2";

        $manifest = "$tmpDir/MANIFEST";
@@ -86,11 +92,31 @@ sub processURL {
    my $hash = `$binDir/nix-hash --flat '$manifest'`
        or die "cannot hash `$manifest'";
    chomp $hash;
+
+    my $urlFile = "$manifestDir/$baseName-$hash.url";
+    open URL, ">$urlFile" or die "cannot create `$urlFile'";
+    print URL "$url";
+    close URL;
    
    my $finalPath = "$manifestDir/$baseName-$hash.nixmanifest";
-    
-    system("@coreutils@/ln", "-sfn", "$manifest", "$finalPath") == 0
+
+    unlink $finalPath if -e $finalPath;
+        
+    symlink("$manifest", "$finalPath")
        or die "cannot link `$finalPath to `$manifest'";
+
+    # Delete all old manifests downloaded from this URL.
+    for my $urlFile2 (glob "$manifestDir/*.url") {
+        next if $urlFile eq $urlFile2;
+        open URL, "<$urlFile2" or die;
+        my $url2 = <URL>;
+        chomp $url2;
+        close URL;
+        next unless $url eq $url2;
+        my $base = $urlFile2; $base =~ s/.url$//;
+        unlink "${base}.url";
+        unlink "${base}.nixmanifest";
+    }
 }

 while (@ARGV) {
--- a/src/libexpr/Makefile.am
+++ b/src/libexpr/Makefile.am
@@ -3,7 +3,7 @@ pkglib_LTLIBRARIES = libexpr.la
 libexpr_la_SOURCES = \
 nixexpr.cc eval.cc primops.cc lexer-tab.cc parser-tab.cc \
 get-drvs.cc attr-path.cc expr-to-xml.cc common-opts.cc \
- names.cc normal-forms.cc
+ names.cc

 pkginclude_HEADERS = \
 nixexpr.hh eval.hh parser.hh lexer-tab.hh parser-tab.hh \
@@ -19,7 +19,7 @@ BUILT_SOURCES = nixexpr-ast.cc nixexpr-ast.hh \
 EXTRA_DIST = lexer.l parser.y nixexpr-ast.def nixexpr-ast.cc

 AM_CXXFLAGS = \
- -I$(srcdir)/.. ${bdb_include} ${aterm_include} \
+ -I$(srcdir)/.. ${aterm_include} \
 -I$(srcdir)/../libutil -I$(srcdir)/../libstore
 AM_CFLAGS = \
 ${aterm_include}
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -16,23 +16,15 @@ namespace nix {
    

 EvalState::EvalState()
-    : sessionNormalForms(32768), normalForms(32768), primOps(128)
+    : normalForms(32768), primOps(128)
 {
-    nrEvaluated = nrCached = nrDepthAfterReset = 0;
+    nrEvaluated = nrCached = 0;

    initNixExprHelpers();

    addPrimOps();

    allowUnsafeEquality = getEnv("NIX_NO_UNSAFE_EQ", "") == "";
-    safeCache = true;
-
-    loadNormalForms();
-}
-
-EvalState::~EvalState()
-{
-    saveNormalForms();
 }


@@ -250,7 +242,7 @@ LocalNoInline(Expr updateAttrs(Expr e1, Expr e2))
 }


-string evalString(EvalState & state, Expr e, PathSet & context)
+string evalString(EvalState & state, Expr e, ATermList & context)
 {
    e = evalExpr(state, e);
    string s;
@@ -262,11 +254,10 @@ string evalString(EvalState & state, Expr e, PathSet & context)

 string evalStringNoCtx(EvalState & state, Expr e)
 {
-    PathSet context;
+    ATermList context;
    string s = evalString(state, e, context);
-    if (!context.empty())
-        throw EvalError(format("the string `%1%' is not allowed to refer to a store path (such as `%2%')")
-            % s % *(context.begin()));
+    if (context != ATempty)
+        throw EvalError(format("the string `%1%' is not allowed to refer to a store path") % s);
    return s;
 }

@@ -320,7 +311,7 @@ ATermList flattenList(EvalState & state, Expr e)
 }


-string coerceToString(EvalState & state, Expr e, PathSet & context,
+string coerceToString(EvalState & state, Expr e, Context & context,
    bool coerceMore, bool copyToStore)
 {
    e = evalExpr(state, e);
@@ -351,7 +342,7 @@ string coerceToString(EvalState & state, Expr e, PathSet & context,
                % path % dstPath);
        }

-        context.insert(dstPath);
+        context.set(toATerm(dstPath), makeNull());
        return dstPath;
    }
        
@@ -359,7 +350,13 @@ string coerceToString(EvalState & state, Expr e, PathSet & context,
    if (matchAttrs(e, es)) {
        Expr e2 = queryAttr(e, "outPath");
        if (!e2) throwTypeError("cannot coerce an attribute set (except a derivation) to a string");
-        return coerceToString(state, e2, context, coerceMore, copyToStore);
+        /* !!! hacky */
+        ATermList c;
+        string s = evalString(state, e2, c);
+        Context c2; matchContext(c, c2);
+        foreach (Context::const_iterator, i, c2)
+            context.set(i->key, e);
+        return s;
    }

    if (coerceMore) {
@@ -393,9 +390,9 @@ string coerceToString(EvalState & state, Expr e, PathSet & context,
 static ATerm concatStrings(EvalState & state, ATermVector & args,
    string separator = "")
 {
-    if (args.empty()) return makeStr("", PathSet());
+    if (args.empty()) return makeStr("", ATempty);
    
-    PathSet context;
+    Context context;
    std::ostringstream s;

    /* If the first element is a path, then the result will also be a
@@ -411,7 +408,7 @@ static ATerm concatStrings(EvalState & state, ATermVector & args,
        s << coerceToString(state, *i, context, false, !isPath);
    }

-    if (isPath && !context.empty())
+    if (isPath && context.size() != 0)
        throw EvalError(format("a string that refers to a store path cannot be appended to a path, in `%1%'")
            % s.str());
    
@@ -421,7 +418,7 @@ static ATerm concatStrings(EvalState & state, ATermVector & args,
 }


-Path coerceToPath(EvalState & state, Expr e, PathSet & context)
+Path coerceToPath(EvalState & state, Expr e, Context & context)
 {
    string path = coerceToString(state, e, context, false, false);
    if (path == "" || path[0] != '/')
@@ -476,10 +473,8 @@ LocalNoInline(Expr evalVar(EvalState & state, ATerm name))
    if (arity == 0)
        /* !!! backtrace for primop call */
        return ((PrimOp) ATgetBlobData(fun)) (state, ATermVector());
-    else {
-        state.safeCache = false;
+    else
        return makePrimOp(arity, fun, ATempty);
-    }
 }


@@ -505,7 +500,6 @@ LocalNoInline(Expr evalCall(EvalState & state, Expr fun, Expr arg))
            for (ATermIterator i(args); i; ++i)
                args2[--arity] = *i;
            /* !!! backtrace for primop call */
-            state.safeCache = true;
            return ((PrimOp) ATgetBlobData(funBlob))
                (state, args2);
        } else
@@ -611,7 +605,7 @@ LocalNoInline(Expr evalPlusConcat(EvalState & state, Expr e))
                    "concatenation of a derivation and a path is deprecated; "
                    "you should write `drv + \"%1%\"' instead of `drv + %1%'")
                % aterm2String(p));
-            PathSet context;
+            Context context;
            return makeStr(
                coerceToString(state, makeSelect(e1, toATerm("outPath")), context)
                + aterm2String(p), context);
@@ -813,19 +807,11 @@ Expr evalExpr(EvalState & state, Expr e)
        format("evaluating expression: %1%") % e);
 #endif

-    const unsigned int hugeEvalExpr = 100;
-    unsigned int nrEvaluated = state.nrEvaluated++;
-    state.nrDepthAfterReset++;
+    state.nrEvaluated++;

    /* Consult the memo table to quickly get the normal form of
       previously evaluated expressions. */
    Expr nf = state.normalForms.get(e);
-    if (nf) {
-        state.nrCached++;
-        return nf;
-    }
-
-    nf = state.sessionNormalForms.get(e);
    if (nf) {
        if (nf == makeBlackHole())
            throwEvalError("infinite recursion encountered");
@@ -834,25 +820,14 @@ Expr evalExpr(EvalState & state, Expr e)
    }

    /* Otherwise, evaluate and memoize. */
-    state.sessionNormalForms.set(e, makeBlackHole());
+    state.normalForms.set(e, makeBlackHole());
    try {
        nf = evalExpr2(state, e);
    } catch (Error & err) {
-        state.sessionNormalForms.remove(e);
+        state.normalForms.remove(e);
        throw;
    }
-
-    // session independent condition
-    if (state.nrDepthAfterReset && state.safeCache &&
-        // heuristic condition
-        state.nrEvaluated - nrEvaluated > hugeEvalExpr) {
-        state.sessionNormalForms.remove(e);
-        state.normalForms.set(e, nf);
-        state.nrDepthAfterReset--;
-    } else {
-        state.sessionNormalForms.set(e, nf);
-    }
-
+    state.normalForms.set(e, nf);
    return nf;
 }

@@ -860,7 +835,6 @@ Expr evalExpr(EvalState & state, Expr e)
 Expr evalFile(EvalState & state, const Path & path)
 {
    startNest(nest, lvlTalkative, format("evaluating file `%1%'") % path);
-    state.nrDepthAfterReset = 0;
    Expr e = parseExprFromFile(state, path);
    try {
        return evalExpr(state, e);
@@ -932,13 +906,11 @@ void printEvalStats(EvalState & state)
    char x;
    bool showStats = getEnv("NIX_SHOW_STATS", "0") != "0";
    printMsg(showStats ? lvlInfo : lvlDebug,
-             format("evaluated %1% expressions, %2% cache hits, %3%%% efficiency, used %4% ATerm bytes, used %5% bytes of stack space, %6% cached normal reduction, %7% session dependent reduction.")
+        format("evaluated %1% expressions, %2% cache hits, %3%%% efficiency, used %4% ATerm bytes, used %5% bytes of stack space")
        % state.nrEvaluated % state.nrCached
        % ((float) state.nrCached / (float) state.nrEvaluated * 100)
        % AT_calcAllocatedSize()
-        % (&x - deepestStack)
-        % state.normalForms.size()
-        % state.sessionNormalForms.size());
+        % (&x - deepestStack));
    if (showStats)
        printATermMapStats();
 }
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -30,7 +30,6 @@ typedef Expr (* PrimOp) (EvalState &, const ATermVector & args);
 struct EvalState 
 {
    ATermMap normalForms;
-    ATermMap sessionNormalForms;
    ATermMap primOps;
    DrvRoots drvRoots;
    DrvHashes drvHashes; /* normalised derivation hashes */
@@ -38,19 +37,14 @@ struct EvalState

    unsigned int nrEvaluated;
    unsigned int nrCached;
-    unsigned int nrDepthAfterReset;

    bool allowUnsafeEquality;
-    bool safeCache;

    EvalState();
-    ~EvalState();

    void addPrimOps();
    void addPrimOp(const string & name,
        unsigned int arity, PrimOp primOp);
-    void loadNormalForms();
-    void saveNormalForms();
 };


@@ -67,7 +61,7 @@ Expr evalFile(EvalState & state, const Path & path);
 Expr strictEvalExpr(EvalState & state, Expr e);

 /* Specific results. */
-string evalString(EvalState & state, Expr e, PathSet & context);
+string evalString(EvalState & state, Expr e, ATermList & context);
 string evalStringNoCtx(EvalState & state, Expr e);
 int evalInt(EvalState & state, Expr e);
 bool evalBool(EvalState & state, Expr e);
@@ -80,13 +74,13 @@ ATermList flattenList(EvalState & state, Expr e);
 /* String coercion.  Converts strings, paths and derivations to a
   string.  If `coerceMore' is set, also converts nulls, integers,
   booleans and lists to a string. */
-string coerceToString(EvalState & state, Expr e, PathSet & context,
+string coerceToString(EvalState & state, Expr e, Context & context,
    bool coerceMore = false, bool copyToStore = true);

 /* Path coercion.  Converts strings, paths and derivations to a path.
   The result is guaranteed to be an canonicalised, absolute path.
   Nothing is copied to the store. */
-Path coerceToPath(EvalState & state, Expr e, PathSet & context);
+Path coerceToPath(EvalState & state, Expr e, Context & context);

 /* Automatically call a function for which each argument has a default
   value or has a binding in the `args' map.  Note: result is a call,
--- a/src/libexpr/expr-to-xml.cc
+++ b/src/libexpr/expr-to-xml.cc
@@ -23,12 +23,12 @@ static XMLAttrs singletonAttrs(const string & name, const string & value)
 typedef set<Expr> ExprSet;


-static void printTermAsXML(Expr e, XMLWriter & doc, PathSet & context,
+static void printTermAsXML(Expr e, XMLWriter & doc, Context & context,
    ExprSet & drvsSeen);


 static void showAttrs(const ATermMap & attrs, XMLWriter & doc,
-    PathSet & context, ExprSet & drvsSeen)
+    Context & context, ExprSet & drvsSeen)
 {
    StringSet names;
    for (ATermMap::const_iterator i = attrs.begin(); i != attrs.end(); ++i)
@@ -65,7 +65,7 @@ static void printPatternAsXML(Pattern pat, XMLWriter & doc)
 }


-static void printTermAsXML(Expr e, XMLWriter & doc, PathSet & context,
+static void printTermAsXML(Expr e, XMLWriter & doc, Context & context,
    ExprSet & drvsSeen)
 {
    XMLAttrs attrs;
@@ -144,7 +144,7 @@ static void printTermAsXML(Expr e, XMLWriter & doc, PathSet & context,
 }


-void printTermAsXML(Expr e, std::ostream & out, PathSet & context)
+void printTermAsXML(Expr e, std::ostream & out, Context & context)
 {
    XMLWriter doc(true, out);
    XMLOpenElement root(doc, "expr");
--- a/src/libexpr/expr-to-xml.hh
+++ b/src/libexpr/expr-to-xml.hh
@@ -9,7 +9,7 @@

 namespace nix {

-void printTermAsXML(Expr e, std::ostream & out, PathSet & context);
+void printTermAsXML(Expr e, std::ostream & out, Context & context);
    
 }

--- a/src/libexpr/get-drvs.cc
+++ b/src/libexpr/get-drvs.cc
@@ -17,7 +17,7 @@ string DrvInfo::queryDrvPath(EvalState & state) const
        if (a && matchPath(evalExpr(state, a), t))
            return aterm2String(t);
        
-        PathSet context;
+        Context context;
        (string &) drvPath = a ? coerceToPath(state, a, context) : "";
    }
    return drvPath;
@@ -29,7 +29,7 @@ string DrvInfo::queryOutPath(EvalState & state) const
    if (outPath == "") {
        Expr a = attrs->get(toATerm("outPath"));
        if (!a) throw TypeError("output path missing");
-        PathSet context;
+        Context context;
        (string &) outPath = coerceToPath(state, a, context);
    }
    return outPath;
@@ -49,7 +49,7 @@ MetaInfo DrvInfo::queryMetaInfo(EvalState & state) const
    for (ATermMap::const_iterator i = attrs2.begin(); i != attrs2.end(); ++i) {
        Expr e = evalExpr(state, i->value);
        string s;
-        PathSet context;
+        ATermList context;
        MetaValue value;
        int n;
        ATermList es;
--- a/src/libexpr/nixexpr-ast.def
+++ b/src/libexpr/nixexpr-ast.def
@@ -45,6 +45,8 @@ Int | int | Expr |
 Str | string ATermList | Expr |
 Str | string | Expr | ObsoleteStr

+ContextElem | string Expr | ContextElem |
+
 # Internal to the parser, doesn't occur in ASTs.
 IndStr | string | Expr |

--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -336,25 +336,47 @@ Expr makeBool(bool b)
 }


-bool matchStr(Expr e, string & s, PathSet & context)
+bool matchStr(Expr e, string & s, ATermList & context)
 {
-    ATermList l;
    ATerm s_;
-
-    if (!matchStr(e, s_, l)) return false;
-
+    if (!matchStr(e, s_, context)) return false;
    s = aterm2String(s_);
-
-    for (ATermIterator i(l); i; ++i)
-        context.insert(aterm2String(*i));
-
    return true;
 }


-Expr makeStr(const string & s, const PathSet & context)
+bool matchStr(Expr e, string & s, Context & context)
 {
-    return makeStr(toATerm(s), toATermList(context));
+    ATermList c;
+    if (!matchStr(e, s, c)) return false;
+    matchContext(c, context);
+    return true;
+}
+
+
+Expr makeStr(const string & s, ATermList context)
+{
+    return makeStr(toATerm(s), context);
+}
+
+
+Expr makeStr(const string & s, const Context & context)
+{
+    ATermList l = ATempty;
+    /* !!! should define a canonical ordering of context elements. */
+    foreach (Context::const_iterator, i, context)
+        l = ATinsert(l, makeContextElem(i->key, i->value));
+    return makeStr(s, l);
+}
+
+
+void matchContext(ATermList context, Context & result)
+{
+    for (ATermIterator i(context); i; ++i) {
+        ATerm s, e;
+        if (!matchContextElem(*i, s, e)) abort();
+        result.set(s, e);
+    }
 }


@@ -380,7 +402,7 @@ string showType(Expr e)

 string showValue(Expr e)
 {
-    PathSet context;
+    ATermList context;
    string s;
    ATerm s2;
    int i;
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -26,6 +26,7 @@ typedef ATerm DefaultValue;
 typedef ATerm Pos;
 typedef ATerm Pattern;
 typedef ATerm ATermBool;
+typedef ATerm ContextElem;


 /* A STL vector of ATerms.  Should be used with great care since it's
@@ -104,11 +105,18 @@ Expr canonicaliseExpr(Expr e);
 Expr makeBool(bool b);


-/* Manipulation of Str() nodes.  Note: matchStr() does not clear
-   context!  */
-bool matchStr(Expr e, string & s, PathSet & context);
+/* Manipulation of Str() nodes. */
+typedef ATermMap Context;

-Expr makeStr(const string & s, const PathSet & context = PathSet());
+bool matchStr(Expr e, string & s, ATermList & context);
+
+bool matchStr(Expr e, string & s, Context & context);
+
+Expr makeStr(const string & s, ATermList context = ATempty);
+
+Expr makeStr(const string & s, const Context & context);
+
+void matchContext(ATermList context, Context & result);


 /* Showing types, values. */
--- a/src/libexpr/normal-forms.cc
+++ b/src/libexpr/normal-forms.cc
@@ -1,64 +0,0 @@
-#include "eval.hh"
-#include "util.hh"
-#include "globals.hh"
-#include "serialise.hh"
-
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-
-namespace nix {
-
-
-void EvalState::loadNormalForms()
-{
-    //    nixCacheFile = getEnv("NIX_CACHE_FILE", nixStateDir + "/reduce-cache");
-    nixCacheFile = getEnv("NIX_CACHE_FILE");
-    string loadFlag = getEnv("NIX_CACHE_FILE_LOAD", "1");
-
-    if(nixCacheFile == "" || loadFlag == "")
-        return;
-    if(!pathExists(nixCacheFile))
-        return;
-
-    printMsg(lvlInfo, format("Load cache: ..."));
-    try {
-        int fd = open(nixCacheFile.c_str(), O_RDONLY);
-        if (fd == -1)
-            throw SysError(format("opening file `%1%'") % nixCacheFile);
-        AutoCloseFD auto_fd = fd;
-
-        FdSource source = fd;
-        normalForms = readATermMap(source);
-    } catch (Error & e) {
-        e.addPrefix(format("Cannot load cached reduce operations from %1%:\n") % nixCacheFile);
-        throw;
-    }
-    printMsg(lvlInfo, format("Load cache: end"));
-}
-
-void EvalState::saveNormalForms()
-{
-    string saveFlag = getEnv("NIX_CACHE_FILE_SAVE", "");
-
-    if(nixCacheFile == "" || saveFlag == "")
-        return;
-
-    printMsg(lvlInfo, format("Save cache: ..."));
-    try {
-        int fd = open(nixCacheFile.c_str(), O_WRONLY | O_TRUNC | O_CREAT, 0666);
-        if (fd == -1)
-            throw SysError(format("opening file `%1%'") % nixCacheFile);
-        AutoCloseFD auto_fd = fd;
-
-        FdSink sink = fd;
-        writeATermMap(normalForms, sink);
-    } catch (Error & e) {
-        e.addPrefix(format("Cannot save cached reduce operations to %1%:\n") % nixCacheFile);
-        throw;
-    }
-    printMsg(lvlInfo, format("Save cache: end"));
-}
-
-
-}
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -74,14 +74,12 @@ static Expr prim_null(EvalState & state, const ATermVector & args)
   platforms. */
 static Expr prim_currentSystem(EvalState & state, const ATermVector & args)
 {
-    state.nrDepthAfterReset = 0;
    return makeStr(thisSystem);
 }


 static Expr prim_currentTime(EvalState & state, const ATermVector & args)
 {
-    state.nrDepthAfterReset = 0;
    return ATmake("Int(<int>)", time(0));
 }

@@ -95,16 +93,17 @@ static Expr prim_currentTime(EvalState & state, const ATermVector & args)
   argument. */ 
 static Expr prim_import(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    Context context;
    Path path = coerceToPath(state, args[0], context);

-    for (PathSet::iterator i = context.begin(); i != context.end(); ++i) {
-        assert(isStorePath(*i));
-        if (!store->isValidPath(*i))
+    foreach (Context::const_iterator, i, context) {
+        Path p = aterm2String(i->key);
+        assert(isStorePath(p));
+        if (!store->isValidPath(p))
            throw EvalError(format("cannot import `%1%', since path `%2%' is not valid")
-                % path % *i);
-        if (isDerivation(*i))
-            store->buildDerivations(singleton<PathSet>(*i));
+                % path % p);
+        if (isDerivation(p))
+            store->buildDerivations(singleton<PathSet>(p));
    }

    return evalFile(state, path);
@@ -138,8 +137,8 @@ static Expr prim_isInt(EvalState & state, const ATermVector & args)
 static Expr prim_isString(EvalState & state, const ATermVector & args)
 {
    string s;
-    PathSet l;
-    return makeBool(matchStr(evalExpr(state, args[0]), s, l));
+    ATermList context;
+    return makeBool(matchStr(evalExpr(state, args[0]), s, context));
 }

 /* Determine whether the argument is an Bool. */
@@ -199,7 +198,7 @@ static Expr prim_genericClosure(EvalState & state, const ATermVector & args)

 static Expr prim_abort(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    ATermList context;
    throw Abort(format("evaluation aborted with the following error message: `%1%'") %
        evalString(state, args[0], context));
 }
@@ -207,7 +206,7 @@ static Expr prim_abort(EvalState & state, const ATermVector & args)

 static Expr prim_throw(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    ATermList context;
    throw ThrownError(format("user-thrown exception: %1%") %
        evalString(state, args[0], context));
 }
@@ -215,7 +214,7 @@ static Expr prim_throw(EvalState & state, const ATermVector & args)

 static Expr prim_addErrorContext(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    ATermList context;
    try {
        return evalExpr(state, args[1]);
    } catch (Error & e) {
@@ -225,12 +224,28 @@ static Expr prim_addErrorContext(EvalState & state, const ATermVector & args)
    }
 }

+/* Try evaluating the argument. Success => {success=true; value=something;}, 
+ * else => {success=false; value=false;} */
+static Expr prim_tryEval(EvalState & state, const ATermVector & args)
+{
+    ATermMap res = ATermMap();
+    try {
+        Expr val = evalExpr(state, args[0]);
+        res.set(toATerm("value"), makeAttrRHS(val, makeNoPos()));
+        res.set(toATerm("success"), makeAttrRHS(eTrue, makeNoPos()));
+    } catch (AssertionError & e) {
+        printMsg(lvlDebug, format("tryEval caught an error: %1%: %2%") % e.prefix() % e.msg());
+        res.set(toATerm("value"), makeAttrRHS(eFalse, makeNoPos()));
+        res.set(toATerm("success"), makeAttrRHS(eFalse, makeNoPos()));
+    }
+    return makeAttrs(res);
+}
+

 /* Return an environment variable.  Use with care. */
 static Expr prim_getEnv(EvalState & state, const ATermVector & args)
 {
    string name = evalStringNoCtx(state, args[0]);
-    state.nrDepthAfterReset = 0;
    return makeStr(getEnv(name));
 }

@@ -242,7 +257,12 @@ static Expr prim_getEnv(EvalState & state, const ATermVector & args)
 static Expr prim_trace(EvalState & state, const ATermVector & args)
 {
    Expr e = evalExpr(state, args[0]);
-    printMsg(lvlError, format("trace: %1%") % e);
+    string s;
+    ATermList context;
+    if (matchStr(e, s, context))
+        printMsg(lvlError, format("trace: %1%") % s);
+    else
+        printMsg(lvlError, format("trace: %1%") % e);
    return evalExpr(state, args[1]);
 }

@@ -319,7 +339,6 @@ static Hash hashDerivationModulo(EvalState & state, Derivation drv)
 static Expr prim_derivationStrict(EvalState & state, const ATermVector & args)
 {
    startNest(nest, lvlVomit, "evaluating derivation");
-    state.nrDepthAfterReset = 0;

    ATermMap attrs;
    queryAllAttrs(evalExpr(state, args[0]), attrs, true);
@@ -342,7 +361,7 @@ static Expr prim_derivationStrict(EvalState & state, const ATermVector & args)
    /* Build the derivation expression by processing the attributes. */
    Derivation drv;
    
-    PathSet context;
+    Context context;

    string outputHash, outputHashAlgo;
    bool outputHashRecursive = false;
@@ -403,8 +422,8 @@ static Expr prim_derivationStrict(EvalState & state, const ATermVector & args)
    /* Everything in the context of the strings in the derivation
       attributes should be added as dependencies of the resulting
       derivation. */
-    foreach (PathSet::iterator, i, context) {
-        Path path = *i;
+    foreach (Context::const_iterator, i, context) {
+        Path path = aterm2String(i->key);
        
        /* Paths marked with `=' denote that the path of a derivation
           is explicitly passed to the builder.  Since that allows the
@@ -422,10 +441,18 @@ static Expr prim_derivationStrict(EvalState & state, const ATermVector & args)
                    drv.inputDrvs[*j] = singleton<StringSet>("out");
            }
        }
-        
-        debug(format("derivation uses `%1%'") % path);
+
+        /* See prim_unsafeDiscardOutputDependency. */
+        bool useDrvAsSrc = false;
+        if (path.at(0) == '~') {
+            path = string(path, 1);
+            useDrvAsSrc = true;
+        }
+
        assert(isStorePath(path));
-        if (isDerivation(path))
+
+        debug(format("derivation uses `%1%'") % path);
+        if (!useDrvAsSrc && isDerivation(path))
            drv.inputDrvs[path] = singleton<StringSet>("out");
        else
            drv.inputSrcs.insert(path);
@@ -499,9 +526,9 @@ static Expr prim_derivationStrict(EvalState & state, const ATermVector & args)
    /* !!! assumes a single output */
    ATermMap outAttrs(2);
    outAttrs.set(toATerm("outPath"),
-        makeAttrRHS(makeStr(outPath, singleton<PathSet>(drvPath)), makeNoPos()));
+        makeAttrRHS(makeStr(outPath, ATmakeList1(makeContextElem(toATerm(drvPath), makeNull()))), makeNoPos()));
    outAttrs.set(toATerm("drvPath"),
-        makeAttrRHS(makeStr(drvPath, singleton<PathSet>("=" + drvPath)), makeNoPos()));
+        makeAttrRHS(makeStr(drvPath, ATmakeList1(makeContextElem(toATerm("=" + drvPath), makeNull()))), makeNoPos()));

    return makeAttrs(outAttrs);
 }
@@ -535,7 +562,7 @@ static Expr prim_derivationLazy(EvalState & state, const ATermVector & args)
 /* Convert the argument to a path.  !!! obsolete? */
 static Expr prim_toPath(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    Context context;
    string path = coerceToPath(state, args[0], context);
    return makeStr(canonPath(path), context);
 }
@@ -551,26 +578,24 @@ static Expr prim_toPath(EvalState & state, const ATermVector & args)
   corner cases. */
 static Expr prim_storePath(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    Context context;
    Path path = canonPath(coerceToPath(state, args[0], context));
-    state.nrDepthAfterReset = 0;
    if (!isInStore(path))
        throw EvalError(format("path `%1%' is not in the Nix store") % path);
    Path path2 = toStorePath(path);
    if (!store->isValidPath(path2))
        throw EvalError(format("store path `%1%' is not valid") % path2);
-    context.insert(path2);
+    context.set(toATerm(path2), makeNull());
    return makeStr(path, context);
 }


 static Expr prim_pathExists(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    Context context;
    Path path = coerceToPath(state, args[0], context);
-    if (!context.empty())
+    if (context.size() != 0)
        throw EvalError(format("string `%1%' cannot refer to other paths") % path);
-    state.nrDepthAfterReset = 0;
    return makeBool(pathExists(path));
 }

@@ -579,7 +604,7 @@ static Expr prim_pathExists(EvalState & state, const ATermVector & args)
   following the last slash. */
 static Expr prim_baseNameOf(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    Context context;
    return makeStr(baseNameOf(coerceToString(state, args[0], context)), context);
 }

@@ -589,7 +614,7 @@ static Expr prim_baseNameOf(EvalState & state, const ATermVector & args)
   of the argument. */
 static Expr prim_dirOf(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    Context context;
    Expr e = evalExpr(state, args[0]); ATerm dummy;
    bool isPath = matchPath(e, dummy);
    Path dir = dirOf(coerceToPath(state, e, context));
@@ -600,11 +625,10 @@ static Expr prim_dirOf(EvalState & state, const ATermVector & args)
 /* Return the contents of a file as a string. */
 static Expr prim_readFile(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    Context context;
    Path path = coerceToPath(state, args[0], context);
-    if (!context.empty())
+    if (context.size() != 0)
        throw EvalError(format("string `%1%' cannot refer to other paths") % path);
-    state.nrDepthAfterReset = 0;
    return makeStr(readFile(path));
 }

@@ -620,7 +644,7 @@ static Expr prim_readFile(EvalState & state, const ATermVector & args)
 static Expr prim_toXML(EvalState & state, const ATermVector & args)
 {
    std::ostringstream out;
-    PathSet context;
+    Context context;
    printTermAsXML(strictEvalExpr(state, args[0]), out, context);
    return makeStr(out.str(), context);
 }
@@ -630,21 +654,21 @@ static Expr prim_toXML(EvalState & state, const ATermVector & args)
   as an input by derivations. */
 static Expr prim_toFile(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    ATermList context;
    string name = evalStringNoCtx(state, args[0]);
    string contents = evalString(state, args[1], context);

    PathSet refs;

-    for (PathSet::iterator i = context.begin(); i != context.end(); ++i) {
-        Path path = *i;
+    Context context2; matchContext(context, context2);
+    foreach (Context::const_iterator, i, context2) {
+        Path path = aterm2String(i->key);
        if (path.at(0) == '=') path = string(path, 1);
        if (isDerivation(path))
            throw EvalError(format("in `toFile': the file `%1%' cannot refer to derivation outputs") % name);
        refs.insert(path);
    }
    
-    state.nrDepthAfterReset = 0;
    Path storePath = readOnlyMode
        ? computeStorePathForText(name, contents, refs)
        : store->addTextToStore(name, contents, refs);
@@ -653,7 +677,7 @@ static Expr prim_toFile(EvalState & state, const ATermVector & args)
       result, since `storePath' itself has references to the paths
       used in args[1]. */
    
-    return makeStr(storePath, singleton<PathSet>(storePath));
+    return makeStr(storePath, ATmakeList1(makeContextElem(toATerm(storePath), makeNull())));
 }


@@ -690,19 +714,18 @@ struct FilterFromExpr : PathFilter

 static Expr prim_filterSource(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    Context context;
    Path path = coerceToPath(state, args[1], context);
-    if (!context.empty())
+    if (context.size() != 0)
        throw EvalError(format("string `%1%' cannot refer to other paths") % path);

    FilterFromExpr filter(state, args[0]);

-    state.nrDepthAfterReset = 0;
    Path dstPath = readOnlyMode
        ? computeStorePathForPath(path, true, htSHA256, filter).first
        : store->addToStore(path, true, htSHA256, filter);

-    return makeStr(dstPath, singleton<PathSet>(dstPath));
+    return makeStr(dstPath, ATmakeList1(makeContextElem(toATerm(dstPath), makeNull())));
 }


@@ -725,7 +748,7 @@ static Expr prim_attrNames(EvalState & state, const ATermVector & args)
    ATermList list = ATempty;
    for (StringSet::const_reverse_iterator i = names.rbegin();
         i != names.rend(); ++i)
-        list = ATinsert(list, makeStr(*i, PathSet()));
+        list = ATinsert(list, makeStr(*i));

    return makeList(list);
 }
@@ -804,6 +827,70 @@ static Expr prim_isAttrs(EvalState & state, const ATermVector & args)
 }


+/* Return the right-biased intersection of two attribute sets as1 and
+   as2, i.e. a set that contains every attribute from as2 that is also
+   a member of as1. */
+static Expr prim_intersectAttrs(EvalState & state, const ATermVector & args)
+{
+    ATermMap as1, as2;
+    queryAllAttrs(evalExpr(state, args[0]), as1, true);
+    queryAllAttrs(evalExpr(state, args[1]), as2, true);
+
+    ATermMap res;
+    foreach (ATermMap::const_iterator, i, as2)
+        if (as1[i->key]) res.set(i->key, i->value);
+
+    return makeAttrs(res);
+}
+
+
+static void attrsInPattern(ATermMap & map, Pattern pat)
+{
+    ATerm name;
+    ATermList formals;
+    Pattern pat1, pat2;
+    ATermBool ellipsis;
+    if (matchAttrsPat(pat, formals, ellipsis)) { 
+        for (ATermIterator i(formals); i; ++i) {
+            ATerm def;
+            if (!matchFormal(*i, name, def)) abort();
+            map.set(name, makeAttrRHS(makeBool(def != constNoDefaultValue), makeNoPos()));
+        }
+    }
+    else if (matchAtPat(pat, pat1, pat2)) {
+        attrsInPattern(map, pat1);
+        attrsInPattern(map, pat2);
+    }
+}
+
+
+/* Return a set containing the names of the formal arguments expected
+   by the function `f'.  The value of each attribute is a Boolean
+   denoting whether has a default value.  For instance,
+
+      functionArgs ({ x, y ? 123}: ...)
+   => { x = false; y = true; }
+
+   "Formal argument" here refers to the attributes pattern-matched by
+   the function.  Plain lambdas are not included, e.g.
+
+      functionArgs (x: ...)
+   => { }
+*/
+static Expr prim_functionArgs(EvalState & state, const ATermVector & args)
+{
+    Expr f = evalExpr(state, args[0]);
+    ATerm pat, body, pos;
+    if (!matchFunction(f, pat, body, pos))
+        throw TypeError("`functionArgs' required a function");
+    
+    ATermMap as;
+    attrsInPattern(as, pat);
+
+    return makeAttrs(as);
+}
+
+
 /*************************************************************
 * Lists
 *************************************************************/
@@ -916,7 +1003,7 @@ static Expr prim_lessThan(EvalState & state, const ATermVector & args)
   `"/nix/store/whatever..."'. */
 static Expr prim_toString(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    Context context;
    string s = coerceToString(state, args[0], context, true, false);
    return makeStr(s, context);
 }
@@ -930,7 +1017,7 @@ static Expr prim_substring(EvalState & state, const ATermVector & args)
 {
    int start = evalInt(state, args[0]);
    int len = evalInt(state, args[1]);
-    PathSet context;
+    Context context;
    string s = coerceToString(state, args[2], context);

    if (start < 0) throw EvalError("negative start position in `substring'");
@@ -941,7 +1028,7 @@ static Expr prim_substring(EvalState & state, const ATermVector & args)

 static Expr prim_stringLength(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    Context context;
    string s = coerceToString(state, args[0], context);
    return makeInt(s.size());
 }
@@ -949,9 +1036,42 @@ static Expr prim_stringLength(EvalState & state, const ATermVector & args)

 static Expr prim_unsafeDiscardStringContext(EvalState & state, const ATermVector & args)
 {
-    PathSet context;
+    Context context;
    string s = coerceToString(state, args[0], context);
-    return makeStr(s, PathSet());
+    return makeStr(s);
+}
+
+
+/* Sometimes we want to pass a derivation path (i.e. pkg.drvPath) to a
+   builder without causing the derivation to be built (for instance,
+   in the derivation that builds NARs in nix-push, when doing
+   source-only deployment).  This primop marks the string context so
+   that builtins.derivation adds the path to drv.inputSrcs rather than
+   drv.inputDrvs. */
+static Expr prim_unsafeDiscardOutputDependency(EvalState & state, const ATermVector & args)
+{
+    Context context;
+    string s = coerceToString(state, args[0], context);
+
+    Context context2;
+    foreach (Context::const_iterator, i, context) {
+        Path p = aterm2String(i->key);
+        if (p.at(0) == '=') p = "~" + string(p, 1);
+        context2.set(toATerm(p), i->value);
+    }
+    
+    return makeStr(s, context2);
+}
+
+
+static Expr prim_queryStringContext(EvalState & state, const ATermVector & args)
+{
+    Context context;
+    string s = coerceToString(state, args[0], context);
+    ATermList l = ATempty;
+    foreach (Context::const_iterator, i, context)
+        l = ATinsert(l, i->value);
+    return makeList(l);
 }


@@ -965,18 +1085,6 @@ static Expr prim_exprToString(EvalState & state, const ATermVector & args)
 }


-static Expr prim_stringToExpr(EvalState & state, const ATermVector & args)
-{
-    /* !!! this can introduce arbitrary garbage terms in the
-       evaluator! */;
-    string s;
-    PathSet l;
-    if (!matchStr(evalExpr(state, args[0]), s, l))
-        throw EvalError("stringToExpr needs string argument!");
-    return ATreadFromString(s.c_str());
-}
-
-
 /*************************************************************
 * Versions
 *************************************************************/
@@ -1029,13 +1137,12 @@ void EvalState::addPrimOps()
    addPrimOp("abort", 1, prim_abort);
    addPrimOp("throw", 1, prim_throw);
    addPrimOp("__addErrorContext", 2, prim_addErrorContext);
+    addPrimOp("__tryEval", 1, prim_tryEval);
    addPrimOp("__getEnv", 1, prim_getEnv);
    addPrimOp("__trace", 2, prim_trace);

-    
    // Expr <-> String
    addPrimOp("__exprToString", 1, prim_exprToString);
-    addPrimOp("__stringToExpr", 1, prim_stringToExpr);

    // Derivations
    addPrimOp("derivation!", 1, prim_derivationStrict);
@@ -1061,6 +1168,8 @@ void EvalState::addPrimOps()
    addPrimOp("__isAttrs", 1, prim_isAttrs);
    addPrimOp("removeAttrs", 2, prim_removeAttrs);
    addPrimOp("__listToAttrs", 1, prim_listToAttrs);
+    addPrimOp("__intersectAttrs", 2, prim_intersectAttrs);
+    addPrimOp("__functionArgs", 1, prim_functionArgs);

    // Lists
    addPrimOp("__isList", 1, prim_isList);
@@ -1081,6 +1190,8 @@ void EvalState::addPrimOps()
    addPrimOp("__substring", 3, prim_substring);
    addPrimOp("__stringLength", 1, prim_stringLength);
    addPrimOp("__unsafeDiscardStringContext", 1, prim_unsafeDiscardStringContext);
+    addPrimOp("__unsafeDiscardOutputDependency", 1, prim_unsafeDiscardOutputDependency);
+    addPrimOp("__queryStringContext", 1, prim_queryStringContext);

    // Versions
    addPrimOp("__parseDrvName", 1, prim_parseDrvName);
--- a/src/libmain/shared.cc
+++ b/src/libmain/shared.cc
@@ -87,18 +87,6 @@ static void setLogType(string lt)
 }


-unsigned long long getIntArg(const string & opt,
-    Strings::iterator & i, const Strings::iterator & end)
-{
-    ++i;
-    if (i == end) throw UsageError(format("`%1%' requires an argument") % opt);
-    long long n;
-    if (!string2Int(*i, n) || n < 0)
-        throw UsageError(format("`%1%' requires a non-negative integer") % opt);
-    return n;
-}
-
-
 void initDerivationsHelpers();


@@ -155,23 +143,29 @@ static void initAndRun(int argc, char * * argv)
    maxSilentTime = queryIntSetting("build-max-silent-time", 0);

    /* Catch SIGINT. */
-    struct sigaction act, oact;
+    struct sigaction act;
    act.sa_handler = sigintHandler;
    sigfillset(&act.sa_mask);
    act.sa_flags = 0;
-    if (sigaction(SIGINT, &act, &oact))
+    if (sigaction(SIGINT, &act, 0))
        throw SysError("installing handler for SIGINT");
-    if (sigaction(SIGTERM, &act, &oact))
+    if (sigaction(SIGTERM, &act, 0))
        throw SysError("installing handler for SIGTERM");
-    if (sigaction(SIGHUP, &act, &oact))
+    if (sigaction(SIGHUP, &act, 0))
        throw SysError("installing handler for SIGHUP");

    /* Ignore SIGPIPE. */
    act.sa_handler = SIG_IGN;
    act.sa_flags = 0;
-    if (sigaction(SIGPIPE, &act, &oact))
+    if (sigaction(SIGPIPE, &act, 0))
        throw SysError("ignoring SIGPIPE");

+    /* Reset SIGCHLD to its default. */
+    act.sa_handler = SIG_DFL;
+    act.sa_flags = 0;
+    if (sigaction(SIGCHLD, &act, 0))
+        throw SysError("resetting SIGCHLD");
+
    /* There is no privacy in the Nix system ;-)  At least not for
       now.  In particular, store objects should be readable by
       everybody.  This prevents nasty surprises when using a shared
@@ -195,7 +189,7 @@ static void initAndRun(int argc, char * * argv)
    for (Strings::iterator i = args.begin(); i != args.end(); ++i) {
        string arg = *i;
        if (string(arg, 0, 4) == "-at-") ;
-        else if (arg.length() > 2 && arg[0] == '-' && arg[1] != '-') {
+        else if (arg.length() > 2 && arg[0] == '-' && arg[1] != '-' && !isdigit(arg[1])) {
            for (unsigned int j = 1; j < arg.length(); j++)
                if (isalpha(arg[j]))
                    remaining.push_back((string) "-" + arg[j]);
@@ -239,11 +233,11 @@ static void initAndRun(int argc, char * * argv)
        else if (arg == "--fallback")
            tryFallback = true;
        else if (arg == "--max-jobs" || arg == "-j")
-            maxBuildJobs = getIntArg(arg, i, args.end());
+            maxBuildJobs = getIntArg<unsigned int>(arg, i, args.end());
        else if (arg == "--readonly-mode")
            readOnlyMode = true;
        else if (arg == "--max-silent-time")
-            maxSilentTime = getIntArg(arg, i, args.end());
+            maxSilentTime = getIntArg<unsigned int>(arg, i, args.end());
        else if (arg == "--no-build-hook")
            useBuildHook = false;
        else if (arg == "--show-trace")
--- a/src/libmain/shared.hh
+++ b/src/libmain/shared.hh
@@ -22,22 +22,30 @@ extern std::string programId;

 namespace nix {

+MakeError(UsageError, nix::Error);
+
 /* Ugh.  No better place to put this. */
 Path makeRootName(const Path & gcRoot, int & counter);
 void printGCWarning();

 void printMissing(const PathSet & paths);

-unsigned long long getIntArg(const string & opt,
-    Strings::iterator & i, const Strings::iterator & end);
+template<class N> N getIntArg(const string & opt,
+    Strings::iterator & i, const Strings::iterator & end)
+{
+    ++i;
+    if (i == end) throw UsageError(format("`%1%' requires an argument") % opt);
+    N n;
+    if (!string2Int(*i, n))
+        throw UsageError(format("`%1%' requires an integer argument") % opt);
+    return n;
+}

 /* Whether we're running setuid. */
 extern bool setuidMode;

 extern volatile ::sig_atomic_t blockInt;

-MakeError(UsageError, nix::Error);
-
 struct RemoveTempRoots 
 {
    ~RemoveTempRoots();    
--- a/src/libstore/Makefile.am
+++ b/src/libstore/Makefile.am
@@ -2,22 +2,22 @@ pkglib_LTLIBRARIES = libstore.la

 libstore_la_SOURCES = \
  store-api.cc local-store.cc remote-store.cc derivations.cc build.cc misc.cc \
-  globals.cc db.cc references.cc pathlocks.cc gc.cc upgrade-schema.cc \
+  globals.cc references.cc pathlocks.cc gc.cc \
  optimise-store.cc

 pkginclude_HEADERS = \
  store-api.hh local-store.hh remote-store.hh derivations.hh misc.hh \
-  globals.hh db.hh references.hh pathlocks.hh \
+  globals.hh references.hh pathlocks.hh \
  worker-protocol.hh

-libstore_la_LIBADD = ../libutil/libutil.la ../boost/format/libformat.la
+libstore_la_LIBADD = ../libutil/libutil.la ../boost/format/libformat.la @ADDITIONAL_NETWORK_LIBS@

 BUILT_SOURCES = derivations-ast.cc derivations-ast.hh

 EXTRA_DIST = derivations-ast.def derivations-ast.cc

 AM_CXXFLAGS = -Wall \
- -I$(srcdir)/.. ${bdb_include} ${aterm_include} -I$(srcdir)/../libutil
+ -I$(srcdir)/.. ${aterm_include} -I$(srcdir)/../libutil

 derivations-ast.cc derivations-ast.hh: ../aterm-helper.pl derivations-ast.def
 	$(perl) $(srcdir)/../aterm-helper.pl derivations-ast.hh derivations-ast.cc < $(srcdir)/derivations-ast.def
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -1,9 +1,12 @@
+#include "config.h"
+
 #include "references.hh"
 #include "pathlocks.hh"
 #include "misc.hh"
 #include "globals.hh"
 #include "local-store.hh"
 #include "util.hh"
+#include "archive.hh"

 #include <map>
 #include <iostream>
@@ -15,19 +18,19 @@

 #include <time.h>
 #include <sys/time.h>
+#include <sys/wait.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <unistd.h>
 #include <errno.h>
+#include <stdio.h>

 #include <pwd.h>
 #include <grp.h>


 /* Includes required for chroot support. */
-#include "config.h"
-
 #if HAVE_SYS_PARAM_H
 #include <sys/param.h>
 #endif
@@ -466,6 +469,8 @@ void UserLock::acquire()
        if (!pw)
            throw Error(format("the user `%1%' in the group `%2%' does not exist")
                % *i % buildUsersGroup);
+
+        createDirs(nixStateDir + "/userpool");
        
        fnUserLock = (format("%1%/userpool/%2%") % nixStateDir % pw->pw_uid).str();

@@ -791,6 +796,9 @@ void DerivationGoal::init()
 {
    trace("init");

+    if (readOnlyMode)
+        throw Error(format("cannot build derivation `%1%' - no write access to the Nix store") % drvPath);
+
    /* The first thing to do is to make sure that the derivation
       exists.  If it doesn't, it may be created through a
       substitute. */
@@ -1310,18 +1318,18 @@ DerivationGoal::HookReply DerivationGoal::tryBuildHook()
        string s;
        foreach (PathSet::iterator, i, allInputs) s += *i + "\n";
        
-        writeStringToFile(inputListFN, s);
+        writeFile(inputListFN, s);

        /* The `outputs' file lists all outputs that have to be copied
           from the remote system. */
        s = "";
        foreach (DerivationOutputs::iterator, i, drv.outputs)
            s += i->second.path + "\n";
-        writeStringToFile(outputListFN, s);
+        writeFile(outputListFN, s);

        /* The `references' file has exactly the format accepted by
           `nix-store --register-validity'. */
-        writeStringToFile(referencesFN,
+        writeFile(referencesFN,
            makeValidityRegistration(allInputs, true, false));

        /* Tell the hook to proceed. */
@@ -1485,7 +1493,7 @@ void DerivationGoal::startBuilder()
        }

        /* Write closure info to `fileName'. */
-        writeStringToFile(tmpDir + "/" + fileName,
+        writeFile(tmpDir + "/" + fileName,
            makeValidityRegistration(paths, false, false));
    }

@@ -1562,7 +1570,7 @@ void DerivationGoal::startBuilder()
           support Samba-in-QEMU. */
        createDirs(chrootRootDir + "/etc");

-        writeStringToFile(chrootRootDir + "/etc/passwd",
+        writeFile(chrootRootDir + "/etc/passwd",
            (format(
                "nixbld:x:%1%:65534:Nix build user:/:/noshell\n"
                "nobody:x:65534:65534:Nobody:/:/noshell\n")
@@ -1600,8 +1608,18 @@ void DerivationGoal::startBuilder()
                dirsInChroot.insert(*i);
            else {
                Path p = chrootRootDir + *i;
-                if (link(i->c_str(), p.c_str()) == -1)
-                    throw SysError(format("linking `%1%' to `%2%'") % p % *i);
+                if (link(i->c_str(), p.c_str()) == -1) {
+                    /* Hard-linking fails if we exceed the maximum
+                       link count on a file (e.g. 32000 of ext3),
+                       which is quite possible after a `nix-store
+                       --optimise'.  Make a copy instead. */
+                    if (errno != EMLINK)
+                        throw SysError(format("linking `%1%' to `%2%'") % p % *i);
+                    StringSink sink;
+                    dumpPath(*i, sink);
+                    StringSource source(sink.s);
+                    restorePath(p, source);
+                }
            }
        }
        
@@ -2107,6 +2125,9 @@ void SubstitutionGoal::init()
        return;
    }

+    if (readOnlyMode)
+        throw Error(format("cannot substitute path `%1%' - no write access to the Nix store") % storePath);
+
    subs = substituters;
    
    tryNext();
--- a/src/libstore/db.cc
+++ b/src/libstore/db.cc
@@ -1,474 +0,0 @@
-#include "config.h"
-
-#ifdef OLD_DB_COMPAT
-
-#include "db.hh"
-#include "util.hh"
-#include "pathlocks.hh"
-
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-#include <errno.h>
-
-#include <memory>
-
-#include <db_cxx.h>
-
-
-namespace nix {
-
-
-/* Wrapper class to ensure proper destruction. */
-class DestroyDbc 
-{
-    Dbc * dbc;
-public:
-    DestroyDbc(Dbc * _dbc) : dbc(_dbc) { }
-    ~DestroyDbc() { dbc->close(); /* close() frees dbc */ }
-};
-
-
-class DestroyDbEnv
-{
-    DbEnv * dbenv;
-public:
-    DestroyDbEnv(DbEnv * _dbenv) : dbenv(_dbenv) { }
-    ~DestroyDbEnv() {
-        if (dbenv) {
-            if (dbenv->get_DB_ENV()) dbenv->close(0);
-            delete dbenv;
-        }
-    }
-    void release() { dbenv = 0; };
-};
-
-
-static void rethrow(DbException & e)
-{
-    throw Error(e.what());
-}
-
-
-Transaction::Transaction()
-    : txn(0)
-{
-}
-
-
-Transaction::Transaction(Database & db)
-    : txn(0)
-{
-    begin(db);
-}
-
-
-Transaction::~Transaction()
-{
-    if (txn) abort();
-}
-
-
-void Transaction::begin(Database & db)
-{
-    assert(txn == 0);
-    db.requireEnv();
-    try {
-        db.env->txn_begin(0, &txn, 0);
-    } catch (DbException e) { rethrow(e); }
-}
-
-
-void Transaction::commit()
-{
-    if (!txn) throw Error("commit called on null transaction");
-    debug(format("committing transaction %1%") % (void *) txn);
-    DbTxn * txn2 = txn;
-    txn = 0;
-    try {
-        txn2->commit(0);
-    } catch (DbException e) { rethrow(e); }
-}
-
-
-void Transaction::abort()
-{
-    if (!txn) throw Error("abort called on null transaction");
-    debug(format("aborting transaction %1%") % (void *) txn);
-    DbTxn * txn2 = txn;
-    txn = 0;
-    try {
-        txn2->abort();
-    } catch (DbException e) { rethrow(e); }
-}
-
-
-void Transaction::moveTo(Transaction & t)
-{
-    if (t.txn) throw Error("target txn already exists");
-    t.txn = txn;
-    txn = 0;
-}
-
-
-void Database::requireEnv()
-{
-    checkInterrupt();
-    if (!env) throw Error("database environment is not open "
-        "(maybe you don't have sufficient permission?)");
-}
-
-
-Db * Database::getDb(TableId table)
-{
-    if (table == 0)
-        throw Error("database table is not open "
-            "(maybe you don't have sufficient permission?)");
-    std::map<TableId, Db *>::iterator i = tables.find(table);
-    if (i == tables.end())
-        throw Error("unknown table id");
-    return i->second;
-}
-
-
-Database::Database()
-    : env(0)
-    , nextId(1)
-{
-}
-
-
-Database::~Database()
-{
-    close();
-}
-
-
-void openEnv(DbEnv * & env, const string & path, u_int32_t flags)
-{
-    try {
-        createDirs(path);
-    } catch (SysError & e) {
-        if (e.errNo == EPERM || e.errNo == EACCES)
-            throw DbNoPermission(format("cannot create the Nix database in `%1%'") % path);
-        else
-            throw;
-    }
-        
-    try {
-        env->open(path.c_str(),
-            DB_INIT_LOCK | DB_INIT_LOG | DB_INIT_MPOOL | DB_INIT_TXN |
-            DB_CREATE | flags,
-            0666);
-    } catch (DbException & e) {
-        printMsg(lvlError, format("environment open failed: %1%") % e.what());
-        throw;
-    }
-}
-
-
-static int my_fsync(int fd)
-{
-    return 0;
-}
-
-
-static void errorPrinter(const DbEnv * env, const char * errpfx, const char * msg)
-{
-    printMsg(lvlError, format("Berkeley DB error: %1%") % msg);
-}
-
-
-static void messagePrinter(const DbEnv * env, const char * msg)
-{
-    printMsg(lvlError, format("Berkeley DB message: %1%") % msg);
-}
-
-
-void Database::open2(const string & path, bool removeOldEnv)
-{
-    if (env) throw Error(format("environment already open"));
-
-    debug(format("opening database environment"));
-
-
-    /* Create the database environment object. */
-    DbEnv * env = new DbEnv(0);
-    DestroyDbEnv deleteEnv(env);
-
-    env->set_errcall(errorPrinter);
-    env->set_msgcall(messagePrinter);
-    if (getEnv("NIX_DEBUG_DB_REGISTER") == "1")
-        env->set_verbose(DB_VERB_REGISTER, 1);
-    env->set_verbose(DB_VERB_RECOVERY, 1);
-    
-    /* Smaller log files. */
-    env->set_lg_bsize(32 * 1024); /* default */
-    env->set_lg_max(256 * 1024); /* must be > 4 * lg_bsize */
-    
-    /* Write the log, but don't sync.  This protects transactions
-       against application crashes, but if the system crashes, some
-       transactions may be undone.  An acceptable risk, I think. */
-    env->set_flags(DB_TXN_WRITE_NOSYNC | DB_LOG_AUTOREMOVE, 1);
-    
-    /* Increase the locking limits.  If you ever get `Dbc::get: Cannot
-       allocate memory' or similar, especially while running
-       `nix-store --verify', just increase the following number, then
-       run db_recover on the database to remove the existing DB
-       environment (since changes only take effect on new
-       environments). */
-    env->set_lk_max_locks(10000);
-    env->set_lk_max_lockers(10000);
-    env->set_lk_max_objects(10000);
-    env->set_lk_detect(DB_LOCK_DEFAULT);
-    
-    /* Dangerous, probably, but from the docs it *seems* that BDB
-       shouldn't sync when DB_TXN_WRITE_NOSYNC is used, but it still
-       fsync()s sometimes. */
-    db_env_set_func_fsync(my_fsync);
-
-    
-    if (removeOldEnv) {
-        printMsg(lvlError, "removing old Berkeley DB database environment...");
-        env->remove(path.c_str(), DB_FORCE);
-        return;
-    }
-
-    openEnv(env, path, DB_REGISTER | DB_RECOVER);
-
-    deleteEnv.release();
-    this->env = env;
-}
-
-
-void Database::open(const string & path)
-{
-    try {
-
-        open2(path, false);
-        
-    } catch (DbException e) {
-        
-        if (e.get_errno() == DB_VERSION_MISMATCH) {
-            /* Remove the environment while we are holding the global
-               lock.  If things go wrong there, we bail out.
-               !!! argh, we abolished the global lock :-( */
-            open2(path, true);
-
-            /* Try again. */
-            open2(path, false);
-
-            /* Force a checkpoint, as per the BDB docs. */
-            env->txn_checkpoint(DB_FORCE, 0, 0);
-
-            printMsg(lvlError, "database succesfully upgraded to new version");
-        }
-
-#if 0        
-        else if (e.get_errno() == DB_RUNRECOVERY) {
-            /* If recovery is needed, do it. */
-            printMsg(lvlError, "running recovery...");
-            open2(path, false, true);
-        }
-#endif        
-        
-        else
-            rethrow(e);
-    }
-}
-
-
-void Database::close()
-{
-    if (!env) return;
-
-    /* Close the database environment. */
-    debug(format("closing database environment"));
-
-    try {
-
-        for (std::map<TableId, Db *>::iterator i = tables.begin();
-             i != tables.end(); )
-        {
-            std::map<TableId, Db *>::iterator j = i;
-            ++j;
-            closeTable(i->first);
-            i = j;
-        }
-
-        /* Do a checkpoint every 128 kilobytes, or every 5 minutes. */
-        env->txn_checkpoint(128, 5, 0);
-        
-        env->close(0);
-
-    } catch (DbException e) { rethrow(e); }
-
-    delete env;
-
-    env = 0;
-}
-
-
-TableId Database::openTable(const string & tableName, bool sorted)
-{
-    requireEnv();
-    TableId table = nextId++;
-
-    try {
-
-        Db * db = new Db(env, 0);
-
-        try {
-            db->open(0, tableName.c_str(), 0, 
-                sorted ? DB_BTREE : DB_HASH,
-                DB_CREATE | DB_AUTO_COMMIT, 0666);
-        } catch (...) {
-            delete db;
-            throw;
-        }
-
-        tables[table] = db;
-
-    } catch (DbException e) { rethrow(e); }
-
-    return table;
-}
-
-
-void Database::closeTable(TableId table)
-{
-    try {
-        Db * db = getDb(table);
-        db->close(DB_NOSYNC);
-        delete db;
-        tables.erase(table);
-    } catch (DbException e) { rethrow(e); }
-}
-
-
-void Database::deleteTable(const string & table)
-{
-    try {
-        env->dbremove(0, table.c_str(), 0, DB_AUTO_COMMIT);
-    } catch (DbException e) { rethrow(e); }
-}
-
-
-bool Database::queryString(const Transaction & txn, TableId table, 
-    const string & key, string & data)
-{
-    checkInterrupt();
-
-    try {
-        Db * db = getDb(table);
-
-        Dbt kt((void *) key.c_str(), key.length());
-        Dbt dt;
-
-        int err = db->get(txn.txn, &kt, &dt, 0);
-        if (err) return false;
-
-        if (!dt.get_data())
-            data = "";
-        else
-            data = string((char *) dt.get_data(), dt.get_size());
-    
-    } catch (DbException e) { rethrow(e); }
-
-    return true;
-}
-
-
-bool Database::queryStrings(const Transaction & txn, TableId table, 
-    const string & key, Strings & data)
-{
-    string d;
-    if (!queryString(txn, table, key, d))
-        return false;
-    data = unpackStrings(d);
-    return true;
-}
-
-
-void Database::setString(const Transaction & txn, TableId table,
-    const string & key, const string & data)
-{
-    checkInterrupt();
-    try {
-        Db * db = getDb(table);
-        Dbt kt((void *) key.c_str(), key.length());
-        Dbt dt((void *) data.c_str(), data.length());
-        db->put(txn.txn, &kt, &dt, 0);
-    } catch (DbException e) { rethrow(e); }
-}
-
-
-void Database::setStrings(const Transaction & txn, TableId table,
-    const string & key, const Strings & data, bool deleteEmpty)
-{
-    if (deleteEmpty && data.size() == 0)
-        delPair(txn, table, key);
-    else
-        setString(txn, table, key, packStrings(data));
-}
-
-
-void Database::delPair(const Transaction & txn, TableId table,
-    const string & key)
-{
-    checkInterrupt();
-    try {
-        Db * db = getDb(table);
-        Dbt kt((void *) key.c_str(), key.length());
-        db->del(txn.txn, &kt, 0);
-        /* Non-existence of a pair with the given key is not an
-           error. */
-    } catch (DbException e) { rethrow(e); }
-}
-
-
-void Database::enumTable(const Transaction & txn, TableId table,
-    Strings & keys, const string & keyPrefix)
-{
-    try {
-        Db * db = getDb(table);
-
-        Dbc * dbc;
-        db->cursor(txn.txn, &dbc, 0);
-        DestroyDbc destroyDbc(dbc);
-
-        Dbt kt, dt;
-        u_int32_t flags = DB_NEXT;
-
-        if (!keyPrefix.empty()) {
-            flags = DB_SET_RANGE;
-            kt = Dbt((void *) keyPrefix.c_str(), keyPrefix.size());
-        }
-
-        while (dbc->get(&kt, &dt, flags) != DB_NOTFOUND) {
-            checkInterrupt();
-            string data((char *) kt.get_data(), kt.get_size());
-            if (!keyPrefix.empty() &&
-                string(data, 0, keyPrefix.size()) != keyPrefix)
-                break;
-            keys.push_back(data);
-            flags = DB_NEXT;
-        }
-
-    } catch (DbException e) { rethrow(e); }
-}
-
- 
-void Database::clearTable(const Transaction & txn, TableId table)
-{
-    try {
-        Db * db = getDb(table);
-        u_int32_t count;
-        db->truncate(txn.txn, &count, 0);
-    } catch (DbException e) { rethrow(e); }
-}
-
-
-}
-
-#endif
--- a/src/libstore/db.hh
+++ b/src/libstore/db.hh
@@ -1,107 +0,0 @@
-#ifndef __DB_H
-#define __DB_H
-
-#include "types.hh"
-
-#include <map>
-
-
-/* Defined externally. */
-class DbTxn;
-class DbEnv;
-class Db;
-
-
-namespace nix {
-
-
-class Database;
-
-
-class Transaction
-{
-    friend class Database;
-
-private:
-    DbTxn * txn;
-    
-public:
-    Transaction();
-    Transaction(Database & _db);
-    ~Transaction();
-
-    void begin(Database & db);
-    void abort();
-    void commit();
-
-    void moveTo(Transaction & t);
-};
-
-
-#define noTxn Transaction()
-
-
-typedef unsigned int TableId; /* table handles */
-
-
-class Database
-{
-    friend class Transaction;
-
-private:
-    DbEnv * env;
-
-    TableId nextId;
-    std::map<TableId, Db *> tables;
-
-    void requireEnv();
-
-    Db * getDb(TableId table);
-
-    void open2(const string & path, bool removeOldEnv);
-    
-public:
-    Database();
-    ~Database();
-    
-    void open(const string & path);
-    void close();
-
-    TableId openTable(const string & table, bool sorted = false);
-    void closeTable(TableId table);
-    void deleteTable(const string & table);
-
-    bool queryString(const Transaction & txn, TableId table, 
-        const string & key, string & data);
-
-    bool queryStrings(const Transaction & txn, TableId table, 
-        const string & key, Strings & data);
-
-    void setString(const Transaction & txn, TableId table,
-        const string & key, const string & data);
-
-    void setStrings(const Transaction & txn, TableId table,
-        const string & key, const Strings & data,
-        bool deleteEmpty = true);
-
-    void delPair(const Transaction & txn, TableId table,
-        const string & key);
-
-    void enumTable(const Transaction & txn, TableId table,
-        Strings & keys, const string & keyPrefix = "");
-
-    void clearTable(const Transaction & txn, TableId table);
-};
-
-
-class DbNoPermission : public Error
-{
-public:
-    DbNoPermission(const format & f) : Error(f) { };
-};
-
- 
-}
-
-
-#endif /* !__DB_H */
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -1,7 +1,7 @@
 #ifndef __DERIVATIONS_H
 #define __DERIVATIONS_H

-typedef struct _ATerm * ATerm;
+#include <aterm1.h>

 #include "hash.hh"

--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -7,6 +7,7 @@

 #include <functional>
 #include <queue>
+#include <algorithm>

 #include <sys/types.h>
 #include <sys/stat.h>
@@ -401,7 +402,7 @@ static void addAdditionalRoots(PathSet & roots)
        if (isInStore(*i)) {
            Path path = toStorePath(*i);
            if (roots.find(path) == roots.end() && store->isValidPath(path)) {
-                debug(format("found additional root `%1%'") % path);
+                debug(format("got additional root `%1%'") % path);
                roots.insert(path);
            }
        }
@@ -439,147 +440,218 @@ Paths topoSortPaths(const PathSet & paths)
 }


-static time_t lastFileAccessTime(const Path & path)
-{
-    checkInterrupt();
-    
-    struct stat st;
-    if (lstat(path.c_str(), &st) == -1)
-        throw SysError(format("statting `%1%'") % path);
-
-    if (S_ISDIR(st.st_mode)) {
-        time_t last = 0;
-	Strings names = readDirectory(path);
-	foreach (Strings::iterator, i, names) {
-            time_t t = lastFileAccessTime(path + "/" + *i);
-            if (t > last) last = t;
-        }
-        return last;
-    }
-
-    else if (S_ISLNK(st.st_mode)) return 0;
-
-    else return st.st_atime;
-}
-
-
 struct GCLimitReached { };


-void LocalStore::gcPath(const GCOptions & options, GCResults & results, 
-    const Path & path)
+struct LocalStore::GCState
 {
-    results.paths.insert(path);
+    GCOptions options;
+    GCResults & results;
+    PathSet roots;
+    PathSet tempRoots;
+    PathSet deleted;
+    PathSet live;
+    PathSet busy;
+    bool gcKeepOutputs;
+    bool gcKeepDerivations;

-    if (!pathExists(path)) return;
-                
-    /* Okay, it's safe to delete. */
-    unsigned long long bytesFreed, blocksFreed;
-    deleteFromStore(path, bytesFreed, blocksFreed);
-    results.bytesFreed += bytesFreed;
-    results.blocksFreed += blocksFreed;
+    bool drvsIndexed;
+    typedef std::multimap<string, Path> DrvsByName;
+    DrvsByName drvsByName; // derivation paths hashed by name attribute

-    if (options.maxFreed && results.bytesFreed > options.maxFreed) {
-        printMsg(lvlInfo, format("deleted more than %1% bytes; stopping") % options.maxFreed);
-        throw GCLimitReached();
-    }
-
-    if (options.maxLinks) {
-        struct stat st;
-        if (stat(nixStore.c_str(), &st) == -1)
-            throw SysError(format("statting `%1%'") % nixStore);
-        if (st.st_nlink < options.maxLinks) {
-            printMsg(lvlInfo, format("link count on the store has dropped below %1%; stopping") % options.maxLinks);
-            throw GCLimitReached();
-        }
-    }
-}
-
-
-void LocalStore::gcPathRecursive(const GCOptions & options,
-    GCResults & results, PathSet & done, const Path & path)
-{
-    if (done.find(path) != done.end()) return;
-    done.insert(path);
-
-    startNest(nest, lvlDebug, format("looking at `%1%'") % path);
-        
-    /* Delete all the referrers first.  They must be garbage too,
-       since if they were live, then the current path would also be
-       live.  Note that deleteFromStore() below still makes sure that
-       the referrer set has become empty, just in case.  (However that
-       doesn't guard against deleting top-level paths that are only
-       reachable from GC roots.) */
-    PathSet referrers;
-    if (isValidPath(path))
-        queryReferrers(path, referrers);
-    foreach (PathSet::iterator, i, referrers)
-        if (*i != path) gcPathRecursive(options, results, done, *i);
-
-    printMsg(lvlInfo, format("deleting `%1%'") % path);
-            
-    gcPath(options, results, path);
-}
-
-
-struct CachingAtimeComparator : public std::binary_function<Path, Path, bool> 
-{
-    std::map<Path, time_t> cache;
-
-    time_t lookup(const Path & p)
+    GCState(GCResults & results_) : results(results_), drvsIndexed(false)
    {
-        std::map<Path, time_t>::iterator i = cache.find(p);
-        if (i != cache.end()) return i->second;
-        debug(format("computing atime of `%1%'") % p);
-        cache[p] = lastFileAccessTime(p);
-        assert(cache.find(p) != cache.end());
-        return cache[p];
-    }
-        
-    bool operator () (const Path & p1, const Path & p2)
-    {
-        return lookup(p2) < lookup(p1);
    }
 };


-static string showTime(const string & format, time_t t)
+static bool doDelete(GCOptions::GCAction action)
 {
-    char s[128];
-    strftime(s, sizeof s, format.c_str(), localtime(&t));
-    return string(s);
+    return action == GCOptions::gcDeleteDead
+        || action == GCOptions::gcDeleteSpecific;
 }


-static bool isLive(const Path & path, const PathSet & livePaths,
-    const PathSet & tempRoots, const PathSet & tempRootsClosed)
+bool LocalStore::isActiveTempFile(const GCState & state,
+    const Path & path, const string & suffix)
 {
-    if (livePaths.find(path) != livePaths.end() ||
-        tempRootsClosed.find(path) != tempRootsClosed.end()) return true;
+    return hasSuffix(path, suffix)
+        && state.tempRoots.find(string(path, 0, path.size() - suffix.size())) != state.tempRoots.end();
+}

-    /* A lock file belonging to a path that we're building right
-       now isn't garbage. */
-    if (hasSuffix(path, ".lock") && tempRoots.find(string(path, 0, path.size() - 5)) != tempRoots.end())
-        return true;

-    /* Don't delete .chroot directories for derivations that are
-       currently being built. */
-    if (hasSuffix(path, ".chroot") && tempRoots.find(string(path, 0, path.size() - 7)) != tempRoots.end())
-        return true;
+/* Return all the derivations in the Nix store that have `path' as an
+   output.  This function assumes that derivations have the same name
+   as their outputs. */
+PathSet LocalStore::findDerivers(GCState & state, const Path & path)
+{
+    PathSet derivers;

+    Path deriver = queryDeriver(path);
+    if (deriver != "") derivers.insert(deriver);
+
+    if (!state.drvsIndexed) {
+        Paths entries = readDirectory(nixStore);
+        foreach (Paths::iterator, i, entries)
+            if (isDerivation(*i))
+                state.drvsByName.insert(std::pair<string, Path>(
+                        getNameOfStorePath(*i), nixStore + "/" + *i));
+        state.drvsIndexed = true;
+    }
+    
+    string name = getNameOfStorePath(path);
+
+    // Urgh, I should have used Haskell...
+    std::pair<GCState::DrvsByName::iterator, GCState::DrvsByName::iterator> range =
+        state.drvsByName.equal_range(name);
+
+    for (GCState::DrvsByName::iterator i = range.first; i != range.second; ++i)
+        if (isValidPath(i->second)) {
+            Derivation drv = derivationFromPath(i->second);
+            foreach (DerivationOutputs::iterator, j, drv.outputs)
+                if (j->second.path == path) derivers.insert(i->second);
+        }
+
+    return derivers;
+}
+
+    
+bool LocalStore::tryToDelete(GCState & state, const Path & path)
+{
+    if (!pathExists(path)) return true;
+    if (state.deleted.find(path) != state.deleted.end()) return true;
+    if (state.live.find(path) != state.live.end()) return false;
+
+    startNest(nest, lvlDebug, format("considering whether to delete `%1%'") % path);
+
+    if (state.roots.find(path) != state.roots.end()) {
+        printMsg(lvlDebug, format("cannot delete `%1%' because it's a root") % path);
+        goto isLive;
+    }
+
+    if (isValidPath(path)) {
+
+        /* Recursively try to delete the referrers of this path.  If
+           any referrer can't be deleted, then this path can't be
+           deleted either. */
+        PathSet referrers;
+        queryReferrers(path, referrers);
+        foreach (PathSet::iterator, i, referrers)
+            if (*i != path && !tryToDelete(state, *i)) {
+                printMsg(lvlDebug, format("cannot delete `%1%' because it has live referrers") % path);
+                goto isLive;
+            }
+
+        /* If gc-keep-derivations is set and this is a derivation,
+           then don't delete the derivation if any of the outputs are
+           live. */
+        if (state.gcKeepDerivations && isDerivation(path)) {
+            Derivation drv = derivationFromPath(path);
+            foreach (DerivationOutputs::iterator, i, drv.outputs)
+                if (!tryToDelete(state, i->second.path)) {
+                    printMsg(lvlDebug, format("cannot delete derivation `%1%' because its output is alive") % path);
+                    goto isLive;
+                }
+        }
+
+        /* If gc-keep-derivations and gc-keep-outputs are both set,
+           it's possible that the path has already been deleted (due
+           to the recursion below), so bail out. */
+        if (!pathExists(path)) return true;
+
+        /* If gc-keep-outputs is set, then don't delete this path if
+           its deriver is not garbage.  !!! Nix does not reliably
+           store derivers, so we have to look at all derivations to
+           determine which of them derive `path'.  Since this makes
+           the garbage collector very slow to start on large Nix
+           stores, here we just look for all derivations that have the
+           same name as `path' (where the name is the part of the
+           filename after the hash, i.e. the `name' attribute of the
+           derivation).  This is somewhat hacky: currently, the
+           deriver of a path always has the same name as the output,
+           but this might change in the future. */
+        if (state.gcKeepOutputs) {
+            PathSet derivers = findDerivers(state, path);
+            foreach (PathSet::iterator, deriver, derivers) {
+                /* Break an infinite recursion if gc-keep-derivations
+                   and gc-keep-outputs are both set by tentatively
+                   assuming that this path is garbage.  This is a safe
+                   assumption because at this point, the only thing
+                   that can prevent it from being garbage is the
+                   deriver.  Since tryToDelete() works "upwards"
+                   through the dependency graph, it won't encouter
+                   this path except in the call to tryToDelete() in
+                   the gc-keep-derivation branch. */
+                state.deleted.insert(path);
+                if (!tryToDelete(state, *deriver)) {
+                    state.deleted.erase(path);
+                    printMsg(lvlDebug, format("cannot delete `%1%' because its deriver `%2%' is alive") % path % *deriver);
+                    goto isLive;
+                }
+            }
+        }
+    }
+
+    else {
+
+        /* A lock file belonging to a path that we're building right
+           now isn't garbage. */
+        if (isActiveTempFile(state, path, ".lock")) return false;
+
+        /* Don't delete .chroot directories for derivations that are
+           currently being built. */
+        if (isActiveTempFile(state, path, ".chroot")) return false;
+
+    }
+
+    /* The path is garbage, so delete it. */
+    if (doDelete(state.options.action)) {
+        printMsg(lvlInfo, format("deleting `%1%'") % path);
+
+        unsigned long long bytesFreed, blocksFreed;
+        deleteFromStore(path, bytesFreed, blocksFreed);
+        state.results.bytesFreed += bytesFreed;
+        state.results.blocksFreed += blocksFreed;
+
+        if (state.options.maxFreed && state.results.bytesFreed > state.options.maxFreed) {
+            printMsg(lvlInfo, format("deleted more than %1% bytes; stopping") % state.options.maxFreed);
+            throw GCLimitReached();
+        }
+
+        if (state.options.maxLinks) {
+            struct stat st;
+            if (stat(nixStore.c_str(), &st) == -1)
+                throw SysError(format("statting `%1%'") % nixStore);
+            if (st.st_nlink < state.options.maxLinks) {
+                printMsg(lvlInfo, format("link count on the store has dropped below %1%; stopping") % state.options.maxLinks);
+                throw GCLimitReached();
+            }
+        }
+        
+    } else
+        printMsg(lvlTalkative, format("would delete `%1%'") % path);
+    
+    state.deleted.insert(path);
+    if (state.options.action != GCOptions::gcReturnLive)
+        state.results.paths.insert(path);
+    return true;
+
+ isLive:
+    state.live.insert(path);
+    if (state.options.action == GCOptions::gcReturnLive)
+        state.results.paths.insert(path);
    return false;
 }


 void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
 {
-    bool gcKeepOutputs =
-        queryBoolSetting("gc-keep-outputs", false);
-    bool gcKeepDerivations =
-        queryBoolSetting("gc-keep-derivations", true);
-    int gcKeepOutputsThreshold = 
-        queryIntSetting ("gc-keep-outputs-threshold", defaultGcLevel);
-
+    GCState state(results);
+    state.options = options;    
+    
+    state.gcKeepOutputs = queryBoolSetting("gc-keep-outputs", false);
+    state.gcKeepDerivations = queryBoolSetting("gc-keep-derivations", true);
+    
    /* Acquire the global GC root.  This prevents
       a) New roots from being added.
       b) Processes from creating new temporary root files. */
@@ -590,198 +662,60 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
    printMsg(lvlError, format("finding garbage collector roots..."));
    Roots rootMap = options.ignoreLiveness ? Roots() : nix::findRoots(true);

-    PathSet roots;
-    foreach (Roots::iterator, i, rootMap) roots.insert(i->second);
+    foreach (Roots::iterator, i, rootMap) state.roots.insert(i->second);

    /* Add additional roots returned by the program specified by the
       NIX_ROOT_FINDER environment variable.  This is typically used
       to add running programs to the set of roots (to prevent them
       from being garbage collected). */
    if (!options.ignoreLiveness)
-        addAdditionalRoots(roots);
-
-    if (options.action == GCOptions::gcReturnRoots) {
-        results.paths = roots;
-        return;
-    }
-
-    /* Determine the live paths which is just the closure of the
-       roots under the `references' relation. */
-    printMsg(lvlError, format("computing live paths..."));
-    PathSet livePaths;
-    foreach (PathSet::const_iterator, i, roots)
-        computeFSClosure(canonPath(*i), livePaths);
-
-    if (gcKeepDerivations) {
-        foreach (PathSet::iterator, i, livePaths) {
-            /* Note that the deriver need not be valid (e.g., if we
-               previously ran the collector with `gcKeepDerivations'
-               turned off). */
-            Path deriver = queryDeriver(*i);
-            if (deriver != "" && isValidPath(deriver))
-                computeFSClosure(deriver, livePaths);
-        }
-    }
-
-    if (gcKeepOutputs) {
-        /* Hmz, identical to storePathRequisites in nix-store. */
-        foreach (PathSet::iterator, i, livePaths)
-            if (isDerivation(*i)) {
-                Derivation drv = derivationFromPath(*i);
-
-		string gcLevelStr = drv.env["__gcLevel"];
-		int gcLevel;
-		if (!string2Int(gcLevelStr, gcLevel))
-		    gcLevel = defaultGcLevel;
-		
-		if (gcLevel >= gcKeepOutputsThreshold)    
-		    foreach (DerivationOutputs::iterator, j, drv.outputs)
-			if (isValidPath(j->second.path))
-			    computeFSClosure(j->second.path, livePaths);
-            }
-    }
-
-    if (options.action == GCOptions::gcReturnLive) {
-        results.paths = livePaths;
-        return;
-    }
+        addAdditionalRoots(state.roots);

    /* Read the temporary roots.  This acquires read locks on all
       per-process temporary root files.  So after this point no paths
       can be added to the set of temporary roots. */
-    PathSet tempRoots;
    FDs fds;
-    readTempRoots(tempRoots, fds);
-
-    /* Close the temporary roots.  Note that we *cannot* do this in
-       readTempRoots(), because there we may not have all locks yet,
-       meaning that an invalid path can become valid (and thus add to
-       the references graph) after we have added it to the closure
-       (and computeFSClosure() assumes that the presence of a path
-       means that it has already been closed). */
-    PathSet tempRootsClosed;
-    foreach (PathSet::iterator, i, tempRoots)
-        if (isValidPath(*i))
-            computeFSClosure(*i, tempRootsClosed);
-        else
-            tempRootsClosed.insert(*i);
+    readTempRoots(state.tempRoots, fds);
+    state.roots.insert(state.tempRoots.begin(), state.tempRoots.end());

    /* After this point the set of roots or temporary roots cannot
       increase, since we hold locks on everything.  So everything
-       that is not currently in in `livePaths' or `tempRootsClosed'
-       can be deleted. */
-    
-    /* Read the Nix store directory to find all currently existing
-       paths and filter out all live paths. */
-    printMsg(lvlError, format("reading the Nix store..."));
-    PathSet storePaths;
-    
-    if (options.action != GCOptions::gcDeleteSpecific) {
-        Paths entries = readDirectory(nixStore);
-        foreach (Paths::iterator, i, entries) {
-            Path path = canonPath(nixStore + "/" + *i);
-            if (!isLive(path, livePaths, tempRoots, tempRootsClosed)) storePaths.insert(path);
-        }
-    }
+       that is not reachable from `roots'. */
+
+    /* Now either delete all garbage paths, or just the specified
+       paths (for gcDeleteSpecific). */
+
+    if (options.action == GCOptions::gcDeleteSpecific) {

-    else {
        foreach (PathSet::iterator, i, options.pathsToDelete) {
            assertStorePath(*i);
-            storePaths.insert(*i);
-            if (isLive(*i, livePaths, tempRoots, tempRootsClosed))
+            if (!tryToDelete(state, *i))
                throw Error(format("cannot delete path `%1%' since it is still alive") % *i);
        }
-    }
-
-    if (options.action == GCOptions::gcReturnDead) {
-        results.paths.insert(storePaths.begin(), storePaths.end());
-        return;
-    }
-
-    /* Delete all dead store paths (or until one of the stop
-       conditions is reached). */
-
-    PathSet done;
-    try {
-
-        if (!options.useAtime) {
-            /* Delete the paths, respecting the partial ordering
-               determined by the references graph. */
-            printMsg(lvlError, format("deleting garbage..."));
-            foreach (PathSet::iterator, i, storePaths)
-                gcPathRecursive(options, results, done, *i);
-        }
-
-        else {
-
-            /* Delete in order of ascending last access time, still
-               maintaining the partial ordering of the reference
-               graph.  Note that we can't use a topological sort for
-               this because that takes time O(V+E), and in this case
-               E=O(V^2) (i.e. the graph is dense because of the edges
-               due to the atime ordering).  So instead we put all
-               deletable paths in a priority queue (ordered by atime),
-               and after deleting a path, add additional paths that
-               have become deletable to the priority queue. */
-
-            CachingAtimeComparator atimeComp;
-
-            /* Create a priority queue that orders paths by ascending
-               atime.  This is why C++ needs type inferencing... */
-            std::priority_queue<Path, vector<Path>, binary_function_ref_adapter<CachingAtimeComparator> > prioQueue =
-                std::priority_queue<Path, vector<Path>, binary_function_ref_adapter<CachingAtimeComparator> >(binary_function_ref_adapter<CachingAtimeComparator>(&atimeComp));
-
-           /* Initially put the paths that are invalid or have no
-              referrers into the priority queue. */
-            printMsg(lvlError, format("finding deletable paths..."));
-            foreach (PathSet::iterator, i, storePaths) {
-                checkInterrupt();
-                /* We can safely delete a path if it's invalid or
-                   it has no referrers.  Note that all the invalid
-                   paths will be deleted in the first round. */
-                if (isValidPath(*i)) {
-                    if (queryReferrersNoSelf(*i).empty()) prioQueue.push(*i);
-                } else prioQueue.push(*i);
-            }
-
-            debug(format("%1% initially deletable paths") % prioQueue.size());
-
-            /* Now delete everything in the order of the priority
-               queue until nothing is left. */
-            printMsg(lvlError, format("deleting garbage..."));
-            while (!prioQueue.empty()) {
-                checkInterrupt();
-                Path path = prioQueue.top(); prioQueue.pop();
-
-                if (options.maxAtime != (time_t) -1 &&
-                    atimeComp.lookup(path) > options.maxAtime)
-                    continue;
-                
-                printMsg(lvlInfo, format("deleting `%1%' (last accessed %2%)") % path % showTime("%F %H:%M:%S", atimeComp.lookup(path)));
-
-                PathSet references;
-                if (isValidPath(path)) references = queryReferencesNoSelf(path);
-
-                gcPath(options, results, path);
-
-                /* For each reference of the current path, see if the
-                   reference has now become deletable (i.e. is in the
-                   set of dead paths and has no referrers left).  If
-                   so add it to the priority queue. */
-                foreach (PathSet::iterator, i, references) {
-                    if (storePaths.find(*i) != storePaths.end() &&
-                        queryReferrersNoSelf(*i).empty())
-                    {
-                        debug(format("path `%1%' has become deletable") % *i);
-                        prioQueue.push(*i);
-                    }
-                }
-            }
-            
-        }
        
-    } catch (GCLimitReached & e) {
-    }
+    } else {
+        
+        printMsg(lvlError, format("reading the Nix store..."));
+        Paths entries = readDirectory(nixStore);
+
+        /* Randomise the order in which we delete entries to make the
+           collector less biased towards deleting paths that come
+           alphabetically first (e.g. /nix/store/000...).  This
+           matters when using --max-freed etc. */
+        vector<Path> entries_(entries.begin(), entries.end());
+        random_shuffle(entries_.begin(), entries_.end());
+
+        if (doDelete(state.options.action))
+            printMsg(lvlError, format("deleting garbage..."));
+        else
+            printMsg(lvlError, format("determining live/dead paths..."));
+    
+        try {
+            foreach (vector<Path>::iterator, i, entries_)
+                tryToDelete(state, canonPath(nixStore + "/" + *i));
+        } catch (GCLimitReached & e) {
+        }
+    }        
 }


--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -13,7 +13,6 @@ string nixDataDir = "/UNINIT";
 string nixLogDir = "/UNINIT";
 string nixStateDir = "/UNINIT";
 string nixDBPath = "/UNINIT";
-string nixCacheFile = "/UNINIT";
 string nixConfDir = "/UNINIT";
 string nixLibexecDir = "/UNINIT";
 string nixBinDir = "/UNINIT";
--- a/src/libstore/globals.hh
+++ b/src/libstore/globals.hh
@@ -24,9 +24,6 @@ extern string nixStateDir;
 /* nixDBPath is the path name of our Berkeley DB environment. */
 extern string nixDBPath;

-/* nixCacheFile is the path name of the normal form cache. */
-extern string nixCacheFile;
-
 /* nixConfDir is the directory where configuration files are
   stored. */
 extern string nixConfDir;
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -16,6 +16,7 @@
 #include <utime.h>
 #include <fcntl.h>
 #include <errno.h>
+#include <stdio.h>


 namespace nix {
@@ -47,8 +48,21 @@ LocalStore::LocalStore()
    
    if (readOnlyMode) return;

+    /* Create missing state directories if they don't already exist. */
    createDirs(nixStore);
-    
+    createDirs(nixDBPath + "/info");
+    createDirs(nixDBPath + "/referrer");
+    createDirs(nixDBPath + "/failed");
+    Path profilesDir = nixStateDir + "/profiles";
+    createDirs(nixStateDir + "/profiles");
+    createDirs(nixStateDir + "/temproots");
+    Path gcRootsDir = nixStateDir + "/gcroots";
+    if (!pathExists(gcRootsDir)) {
+        createDirs(gcRootsDir);
+        if (symlink(profilesDir.c_str(), (gcRootsDir + "/profiles").c_str()) == -1)
+            throw SysError(format("creating symlink to `%1%'") % profilesDir);
+    }
+  
    checkStoreNotSymlink();

    try {
@@ -64,11 +78,7 @@ LocalStore::LocalStore()
        printMsg(lvlError, "waiting for the big Nix store lock...");
        lockFile(globalLock, ltRead, true);
    }
-
-    createDirs(nixDBPath + "/info");
-    createDirs(nixDBPath + "/referrer");
-    createDirs(nixDBPath + "/failed");
-
+    
    int curSchema = getSchema();
    if (curSchema > nixSchemaVersion)
        throw Error(format("current Nix store schema is version %1%, but I only support %2%")
@@ -79,6 +89,8 @@ LocalStore::LocalStore()
    }
    if (curSchema == 1) throw Error("your Nix store is no longer supported");
    if (curSchema < nixSchemaVersion) upgradeStore12();
+
+    doFsync = queryBoolSetting("fsync-metadata", false);
 }


@@ -212,7 +224,7 @@ static Path tmpFileForAtomicUpdate(const Path & path)
 }


-static void appendReferrer(const Path & from, const Path & to, bool lock)
+void LocalStore::appendReferrer(const Path & from, const Path & to, bool lock)
 {
    Path referrersFile = referrersFileFor(from);
    
@@ -227,6 +239,8 @@ static void appendReferrer(const Path & from, const Path & to, bool lock)
    
    string s = " " + to;
    writeFull(fd, (const unsigned char *) s.c_str(), s.size());
+
+    if (doFsync) fdatasync(fd);
 }


@@ -257,6 +271,8 @@ void LocalStore::rewriteReferrers(const Path & path, bool purge, PathSet referre
    
    writeFull(fd, (const unsigned char *) s.c_str(), s.size());

+    if (doFsync) fdatasync(fd);
+    
    fd.close(); /* for Windows; can't rename open file */

    if (rename(tmpFile.c_str(), referrersFile.c_str()) == -1)
@@ -337,7 +353,7 @@ void LocalStore::registerValidPath(const ValidPathInfo & info, bool ignoreValidi

    /* Atomically rewrite the info file. */
    Path tmpFile = tmpFileForAtomicUpdate(infoFile);
-    writeFile(tmpFile, s);
+    writeFile(tmpFile, s, doFsync);
    if (rename(tmpFile.c_str(), infoFile.c_str()) == -1)
        throw SysError(format("cannot rename `%1%' to `%2%'") % tmpFile % infoFile);

@@ -380,6 +396,9 @@ ValidPathInfo LocalStore::queryPathInfo(const Path & path, bool ignoreErrors)

    assertStorePath(path);

+    if (!isValidPath(path))
+        throw Error(format("path `%1%' is not valid") % path);
+
    std::map<Path, ValidPathInfo>::iterator lookup = pathInfoCache.find(path);
    if (lookup != pathInfoCache.end()) return lookup->second;
    
@@ -394,7 +413,11 @@ ValidPathInfo LocalStore::queryPathInfo(const Path & path, bool ignoreErrors)

    foreach (Strings::iterator, i, lines) {
        string::size_type p = i->find(':');
-        if (p == string::npos) continue; /* bad line */
+        if (p == string::npos) {
+            if (!ignoreErrors)
+                throw Error(format("corrupt line in `%1%': %2%") % infoFile % *i);
+            continue; /* bad line */
+        }
        string name(*i, 0, p);
        string value(*i, p + 2);
        if (name == "References") {
@@ -425,7 +448,22 @@ bool LocalStore::isValidPath(const Path & path)
    /* Files in the info directory starting with a `.' are temporary
       files. */
    if (baseNameOf(path).at(0) == '.') return false;
-    return pathExists(infoFileFor(path));
+
+    /* A path is valid if its info file exists and has a non-zero
+       size.  (The non-zero size restriction is to be robust to
+       certain kinds of filesystem corruption, particularly with
+       ext4.) */
+    Path infoFile = infoFileFor(path);
+
+    struct stat st;
+    if (lstat(infoFile.c_str(), &st)) {
+        if (errno == ENOENT) return false;
+        throw SysError(format("getting status of `%1%'") % infoFile);
+    }
+
+    if (st.st_size == 0) return false;
+    
+    return true;
 }


@@ -509,6 +547,13 @@ void LocalStore::startSubstituter(const Path & substituter, RunningSubstituter &

    case 0: /* child */
        try {
+            /* Hack to let "make check" succeed on Darwin.  The
+               libtool wrapper script sets DYLD_LIBRARY_PATH to our
+               libutil (among others), but Perl also depends on a
+               library named libutil.  As a result, substituters
+               written in Perl (i.e. all of them) fail. */
+            unsetenv("DYLD_LIBRARY_PATH");
+            
            fromPipe.readSide.close();
            toPipe.writeSide.close();
            if (dup2(toPipe.readSide, STDIN_FILENO) == -1)
@@ -698,7 +743,7 @@ Path LocalStore::addToStoreFromDump(const string & dump, const string & name,
                StringSource source(dump);
                restorePath(dstPath, source);
            } else
-                writeStringToFile(dstPath, dump);
+                writeFile(dstPath, dump);

            canonicalisePathMetaData(dstPath);

@@ -753,7 +798,7 @@ Path LocalStore::addTextToStore(const string & name, const string & s,

            if (pathExists(dstPath)) deletePathWrapped(dstPath);

-            writeStringToFile(dstPath, s);
+            writeFile(dstPath, s);

            canonicalisePathMetaData(dstPath);
            
@@ -832,7 +877,7 @@ void LocalStore::exportPath(const Path & path, bool sign,
        Path tmpDir = createTempDir();
        AutoDelete delTmp(tmpDir);
        Path hashFile = tmpDir + "/hash";
-        writeStringToFile(hashFile, printHash(hash));
+        writeFile(hashFile, printHash(hash));

        Path secretKey = nixConfDir + "/signing-key.sec";
        checkSecrecy(secretKey);
@@ -908,7 +953,7 @@ Path LocalStore::importPath(bool requireSignature, Source & source)

        if (requireSignature) {
            Path sigFile = tmpDir + "/sig";
-            writeStringToFile(sigFile, signature);
+            writeFile(sigFile, signature);

            Strings args;
            args.push_back("rsautl");
@@ -1011,8 +1056,18 @@ void LocalStore::verifyStore(bool checkContents)
        } else if (!pathExists(*i)) {
            printMsg(lvlError, format("path `%1%' disappeared") % *i);
            invalidatePath(*i);
-        } else
-            validPaths.insert(*i);
+        } else {
+            Path infoFile = infoFileFor(*i);
+            struct stat st;
+            if (lstat(infoFile.c_str(), &st))
+                throw SysError(format("getting status of `%1%'") % infoFile);
+            if (st.st_size == 0) {
+                printMsg(lvlError, format("removing corrupt info file `%1%'") % infoFile);
+                if (unlink(infoFile.c_str()) == -1)
+                    throw SysError(format("unlinking `%1%'") % infoFile);
+            }
+            else validPaths.insert(*i);
+        }
    }


@@ -1116,4 +1171,16 @@ void LocalStore::verifyStore(bool checkContents)
 }


+/* Upgrade from schema 4 (Nix 0.11) to schema 5 (Nix >= 0.12).  The
+   old schema uses Berkeley DB, the new one stores store path
+   meta-information in files. */
+void LocalStore::upgradeStore12()
+{
+    throw Error(
+        "Your Nix store has a database in Berkeley DB format,\n"
+        "which is no longer supported. To convert to the new format,\n"
+        "please upgrade Nix to version 0.12 first.");
+}
+
+
 }
--- a/src/libstore/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -158,12 +158,17 @@ private:
    /* Store paths for which the referrers file must be purged. */
    PathSet delayedUpdates;

+    /* Whether to do an fsync() after writing Nix metadata. */
+    bool doFsync;
+
    int getSchema();

    void registerValidPath(const ValidPathInfo & info, bool ignoreValidity = false);

    ValidPathInfo queryPathInfo(const Path & path, bool ignoreErrors = false);

+    void appendReferrer(const Path & from, const Path & to, bool lock);
+    
    void rewriteReferrers(const Path & path, bool purge, PathSet referrers);

    void flushDelayedUpdates();
@@ -174,20 +179,20 @@ private:
    
    void upgradeStore12();

-    void gcPath(const GCOptions & options, GCResults & results,
-        const Path & path);
-
-    void gcPathRecursive(const GCOptions & options,
-        GCResults & results, PathSet & done, const Path & path);
+    struct GCState;

+    bool tryToDelete(GCState & state, const Path & path);
+    
+    PathSet findDerivers(GCState & state, const Path & path);
+    
+    bool isActiveTempFile(const GCState & state,
+        const Path & path, const string & suffix);
+        
    void startSubstituter(const Path & substituter,
        RunningSubstituter & runningSubstituter);
 };


-/* Copy a path recursively. */
-void copyPath(const Path & src, const Path & dst);
-
 /* "Fix", or canonicalise, the meta-data of the files in a store path
   after it has been built.  In particular:
   - the last modification date on each file is set to 1 (i.e.,
--- a/src/libstore/misc.cc
+++ b/src/libstore/misc.cc
@@ -19,7 +19,7 @@ Derivation derivationFromPath(const Path & drvPath)


 void computeFSClosure(const Path & storePath,
-    PathSet & paths, bool flipDirection)
+    PathSet & paths, bool flipDirection, bool includeOutputs)
 {
    if (paths.find(storePath) != paths.end()) return;
    paths.insert(storePath);
@@ -30,8 +30,15 @@ void computeFSClosure(const Path & storePath,
    else
        store->queryReferences(storePath, references);

+    if (includeOutputs && isDerivation(storePath)) {
+        Derivation drv = derivationFromPath(storePath);
+        foreach (DerivationOutputs::iterator, i, drv.outputs)
+            if (store->isValidPath(i->second.path))
+                computeFSClosure(i->second.path, paths, flipDirection, true);
+    }
+
    foreach (PathSet::iterator, i, references)
-        computeFSClosure(*i, paths, flipDirection);
+        computeFSClosure(*i, paths, flipDirection, includeOutputs);
 }


--- a/src/libstore/misc.hh
+++ b/src/libstore/misc.hh
@@ -19,7 +19,8 @@ Derivation derivationFromPath(const Path & drvPath);
   `referrers' relation instead of the `references' relation is
   returned. */
 void computeFSClosure(const Path & storePath,
-    PathSet & paths, bool flipDirection = false);
+    PathSet & paths, bool flipDirection = false,
+    bool includeOutputs = false);

 /* Return the path corresponding to the output identifier `id' in the
   given derivation. */
--- a/src/libstore/optimise-store.cc
+++ b/src/libstore/optimise-store.cc
@@ -5,6 +5,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 #include <errno.h>
+#include <stdio.h>


 namespace nix {
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -426,8 +426,9 @@ void RemoteStore::collectGarbage(const GCOptions & options, GCResults & results)
    writeLongLong(options.maxFreed, to);
    writeInt(options.maxLinks, to);
    if (GET_PROTOCOL_MINOR(daemonVersion) >= 5) {
-        writeInt(options.useAtime, to);
-        writeInt(options.maxAtime, to);
+        /* removed options */
+        writeInt(0, to);
+        writeInt(0, to);
    }
    
    processStderr();
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -1,6 +1,7 @@
 #include "store-api.hh"
 #include "globals.hh"
 #include "util.hh"
+#include "derivations.hh"

 #include <limits.h>

@@ -14,8 +15,6 @@ GCOptions::GCOptions()
    ignoreLiveness = false;
    maxFreed = 0;
    maxLinks = 0;
-    useAtime = false;
-    maxAtime = (time_t) -1;
 }


@@ -54,6 +53,18 @@ Path toStorePath(const Path & path)
 }


+string getNameOfStorePath(const Path & path)
+{
+    Path::size_type slash = path.rfind('/');
+    string p = slash == Path::npos ? path : string(path, slash + 1);
+    Path::size_type dash = p.find('-');
+    assert(dash != Path::npos);
+    string p2 = string(p, dash + 1);
+    if (isDerivation(p2)) p2 = string(p2, 0, p2.size() - 4);
+    return p2;
+}
+
+
 Path followLinksToStore(const Path & _path)
 {
    Path path = absPath(_path);
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -22,10 +22,6 @@ struct GCOptions
 {
    /* Garbage collector operation:

-       - `gcReturnRoots': find and return the set of roots for the
-         garbage collector.  These are the store paths symlinked to in
-         the `gcroots' directory.
-
       - `gcReturnLive': return the set of paths reachable from
         (i.e. in the closure of) the roots.

@@ -38,7 +34,6 @@ struct GCOptions
          `pathsToDelete', insofar as they are not reachable.
    */
    typedef enum {
-        gcReturnRoots,
        gcReturnLive,
        gcReturnDead,
        gcDeleteDead,
@@ -64,22 +59,6 @@ struct GCOptions
       has dropped below `maxLinks'. */
    unsigned int maxLinks;

-    /* Delete paths in order of ascending last access time.  I.e.,
-       prefer deleting unrecently used paths.  Useful in conjunction
-       with `maxFreed' and `maxLinks' (or manual interruption).  The
-       access time of a path is defined as the highest atime of any
-       non-directory, non-symlink file under that path.  Directories
-       and symlinks are ignored because their atimes are frequently
-       mass-updated, e.g. by `locate'.  Note that optimiseStore()
-       somewhat reduces the usefulness of this option: it hard-links
-       regular files and symlink together, giving them a "shared"
-       atime. */
-    bool useAtime;
-
-    /* Do not delete paths newer than `maxAtime'.  -1 means no age
-       limit. */
-    time_t maxAtime;
-
    GCOptions();
 };

@@ -264,6 +243,12 @@ void checkStoreName(const string & name);
 Path toStorePath(const Path & path);


+/* Get the "name" part of a store path, that is, the part after the
+   hash and the dash, and with any ".drv" suffix removed
+   (e.g. /nix/store/<hash>-foo-1.2.3.drv => foo-1.2.3). */
+string getNameOfStorePath(const Path & path);
+
+
 /* Follow symlinks until we end up with a path in the Nix store. */
 Path followLinksToStore(const Path & path);

--- a/src/libstore/upgrade-schema.cc
+++ b/src/libstore/upgrade-schema.cc
@@ -1,108 +0,0 @@
-#include "db.hh"
-#include "hash.hh"
-#include "util.hh"
-#include "local-store.hh"
-#include "globals.hh"
-#include "pathlocks.hh"
-#include "config.h"
-
-#include <iostream>
-
-
-namespace nix {
-
-
-Hash parseHashField(const Path & path, const string & s);
-
-
-/* Upgrade from schema 4 (Nix 0.11) to schema 5 (Nix >= 0.12).  The
-   old schema uses Berkeley DB, the new one stores store path
-   meta-information in files. */
-void LocalStore::upgradeStore12()
-{
-#if OLD_DB_COMPAT
-    
-#ifdef __CYGWIN__
-    /* Cygwin can't upgrade a read lock to a write lock... */
-    lockFile(globalLock, ltNone, true);
-#endif
-
-    if (!lockFile(globalLock, ltWrite, false)) {
-        printMsg(lvlError, "waiting for exclusive access to the Nix store...");
-        lockFile(globalLock, ltWrite, true);
-    }
-
-    printMsg(lvlError, "upgrading Nix store to new schema (this may take a while)...");
-
-    if (getSchema() >= nixSchemaVersion) return; /* somebody else beat us to it */
-
-    /* Open the old Nix database and tables. */
-    Database nixDB;
-    nixDB.open(nixDBPath);
-    
-    /* dbValidPaths :: Path -> ()
-
-       The existence of a key $p$ indicates that path $p$ is valid
-       (that is, produced by a succesful build). */
-    TableId dbValidPaths = nixDB.openTable("validpaths");
-
-    /* dbReferences :: Path -> [Path]
-
-       This table lists the outgoing file system references for each
-       output path that has been built by a Nix derivation.  These are
-       found by scanning the path for the hash components of input
-       paths. */
-    TableId dbReferences = nixDB.openTable("references");
-
-    /* dbReferrers :: Path -> Path
-
-       This table is just the reverse mapping of dbReferences.  This
-       table can have duplicate keys, each corresponding value
-       denoting a single referrer. */
-    // Not needed for conversion: it's just the inverse of
-    // references.
-    // TableId dbReferrers = nixDB.openTable("referrers");
-
-    /* dbDerivers :: Path -> [Path]
-
-       This table lists the derivation used to build a path.  There
-       can only be multiple such paths for fixed-output derivations
-       (i.e., derivations specifying an expected hash). */
-    TableId dbDerivers = nixDB.openTable("derivers");
-
-    Paths paths;
-    nixDB.enumTable(noTxn, dbValidPaths, paths);
-    
-    foreach (Paths::iterator, i, paths) {
-        ValidPathInfo info;
-        info.path = *i;
-        
-        Paths references;
-        nixDB.queryStrings(noTxn, dbReferences, *i, references);
-        info.references.insert(references.begin(), references.end());
-        
-        string s;
-        nixDB.queryString(noTxn, dbValidPaths, *i, s);
-        info.hash = parseHashField(*i, s);
-        
-        nixDB.queryString(noTxn, dbDerivers, *i, info.deriver);
-        
-        registerValidPath(info, true);
-        std::cerr << ".";
-    }
-
-    std::cerr << std::endl;
-
-    writeFile(schemaPath, (format("%1%") % nixSchemaVersion).str());
-
-    lockFile(globalLock, ltRead, true);
-
-#else
-    throw Error(
-        "Your Nix store has a database in Berkeley DB format. To convert\n"
-        "to the new format, please compile Nix with Berkeley DB support.");
-#endif
-}
-
-
-}
--- a/src/libutil/archive.cc
+++ b/src/libutil/archive.cc
@@ -1,3 +1,5 @@
+#include "config.h"
+
 #include <cerrno>
 #include <algorithm>
 #include <vector>
@@ -12,8 +14,6 @@
 #include "archive.hh"
 #include "util.hh"

-#include "config.h"
-

 namespace nix {

@@ -302,7 +302,12 @@ struct RestoreSink : ParseSink
 #if HAVE_POSIX_FALLOCATE
        if (len) {
            errno = posix_fallocate(fd, 0, len);
-            if (errno) throw SysError(format("preallocating file of %1% bytes") % len);
+            /* Note that EINVAL may indicate that the underlying
+               filesystem doesn't support preallocation (e.g. on
+               OpenSolaris).  Since preallocation is just an
+               optimisation, ignore it. */
+            if (errno && errno != EINVAL)
+                throw SysError(format("preallocating file of %1% bytes") % len);
        }
 #endif
    }
--- a/src/libutil/aterm-map.cc
+++ b/src/libutil/aterm-map.cc
@@ -215,7 +215,7 @@ void ATermMap::remove(ATerm key)
 }


-unsigned int ATermMap::size() const
+unsigned int ATermMap::size()
 {
    return count; /* STL nomenclature */
 }
--- a/src/libutil/aterm-map.hh
+++ b/src/libutil/aterm-map.hh
@@ -1,8 +1,8 @@
 #ifndef __ATERM_MAP_H
 #define __ATERM_MAP_H

-typedef struct _ATerm * ATerm;
-
+#include <aterm1.h>
+#include <aterm2.h>
 #include <assert.h>


@@ -59,7 +59,7 @@ public:

    void remove(ATerm key);

-    unsigned int size() const;
+    unsigned int size();

    struct const_iterator
    {
--- a/src/libutil/serialise.cc
+++ b/src/libutil/serialise.cc
@@ -1,9 +1,9 @@
 #include "serialise.hh"
 #include "util.hh"
-#include "aterm.hh"

 #include <cstring>

+
 namespace nix {


@@ -73,67 +73,6 @@ void writeStringSet(const StringSet & ss, Sink & sink)
 }


-void writeATerm(ATerm t, Sink & sink)
-{
-    int len;
-    unsigned char *buf = (unsigned char *) ATwriteToBinaryString(t, &len);
-    AutoDeleteArray<unsigned char> d(buf);
-    writeInt(len, sink);
-    sink(buf, len);
-}
-
-
-/* convert the ATermMap to a list of couple because many terms are shared
-   between the keys and between the values.  Thus the BAF stored by
-   writeATerm consume less memory space.  The list of couples is saved
-   inside a tree structure of /treedepth/ height because the serialiasation
-   of ATerm cause a tail recurssion on list tails. */
-void writeATermMap(const ATermMap & tm, Sink & sink)
-{
-    const unsigned int treedepth = 5;
-    const unsigned int maxarity = 128; // 2 < maxarity < MAX_ARITY (= 255)
-    const unsigned int bufsize = treedepth * maxarity;
-
-    AFun map = ATmakeAFun("map", 2, ATfalse);
-    AFun node = ATmakeAFun("node", maxarity, ATfalse);
-    ATerm empty = (ATerm) ATmakeAppl0(ATmakeAFun("empty", 0, ATfalse));
-
-    unsigned int c[treedepth];
-    ATerm *buf = new ATerm[bufsize];
-    AutoDeleteArray<ATerm> d(buf);
-
-    memset(buf, 0, bufsize * sizeof(ATerm));
-    ATprotectArray(buf, bufsize);
-
-    for (unsigned int j = 0; j < treedepth; j++)
-        c[j] = 0;
-
-    for (ATermMap::const_iterator i = tm.begin(); i != tm.end(); ++i) {
-         unsigned int depth = treedepth - 1;
-         ATerm term = (ATerm) ATmakeAppl2(map, i->key, i->value);
-         buf[depth * maxarity + c[depth]++] = term;
-         while (c[depth] % maxarity == 0) {
-             c[depth] = 0;
-             term = (ATerm) ATmakeApplArray(node, &buf[depth * maxarity]);
-             depth--;
-             buf[depth * maxarity + c[depth]++] = term;
-         }
-    }
-
-    unsigned int depth = treedepth;
-    ATerm last_node = empty;
-    while (depth--) {
-        buf[depth * maxarity + c[depth]++] = last_node;
-        while (c[depth] % maxarity)
-            buf[depth * maxarity + c[depth]++] = empty;
-        last_node = (ATerm) ATmakeApplArray(node, &buf[depth * maxarity]);
-    }
-
-    writeATerm(last_node, sink);
-    ATunprotectArray(buf);
-}
-
-
 void readPadding(unsigned int len, Source & source)
 {
    if (len % 8) {
@@ -197,48 +136,4 @@ StringSet readStringSet(Source & source)
 }


-ATerm readATerm(Source & source)
-{
-    unsigned int len = readInt(source);
-    unsigned char * buf = new unsigned char[len];
-    AutoDeleteArray<unsigned char> d(buf);
-    source(buf, len);
-    ATerm t = ATreadFromBinaryString((char *) buf, len);
-    if (t == 0)
-        throw SerialisationError("cannot read a valid ATerm.");
-    return t;
-}
-
-
-static void recursiveInitATermMap(ATermMap &tm, bool &stop, ATermAppl node)
-{
-    const unsigned int arity = ATgetArity(ATgetAFun(node));
-    ATerm key, value;
-
-    switch (arity) {
-        case 0:
-            stop = true;
-            return;
-        case 2:
-            key = ATgetArgument(node, 0);
-            value = ATgetArgument(node, 1);
-            tm.set(key, value);
-            return;
-        default:
-            for (unsigned int i = 0; i < arity && !stop; i++)
-              recursiveInitATermMap(tm, stop, (ATermAppl) ATgetArgument(node, i));
-            return;
-    }
-}
-
-ATermMap readATermMap(Source & source)
-{
-    ATermMap tm;
-    bool stop = false;
-
-    recursiveInitATermMap(tm, stop, (ATermAppl) readATerm(source));
-    return tm;
-}
-
-
 }
--- a/src/libutil/serialise.hh
+++ b/src/libutil/serialise.hh
@@ -2,7 +2,7 @@
 #define __SERIALISE_H

 #include "types.hh"
-#include "aterm-map.hh"
+

 namespace nix {

@@ -98,16 +98,12 @@ void writeInt(unsigned int n, Sink & sink);
 void writeLongLong(unsigned long long n, Sink & sink);
 void writeString(const string & s, Sink & sink);
 void writeStringSet(const StringSet & ss, Sink & sink);
-void writeATerm(ATerm t, Sink & sink);
-void writeATermMap(const ATermMap & tm, Sink & sink);

 void readPadding(unsigned int len, Source & source);
 unsigned int readInt(Source & source);
 unsigned long long readLongLong(Source & source);
 string readString(Source & source);
 StringSet readStringSet(Source & source);
-ATerm readATerm(Source & source);
-ATermMap readATermMap(Source & source);


 MakeError(SerialisationError, Error)
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -15,6 +15,7 @@
 #include <sys/wait.h>
 #include <sys/types.h>
 #include <fcntl.h>
+#include <unistd.h>

 #include "util.hh"

@@ -220,12 +221,13 @@ string readFile(const Path & path)
 }


-void writeFile(const Path & path, const string & s)
+void writeFile(const Path & path, const string & s, bool doFsync)
 {
    AutoCloseFD fd = open(path.c_str(), O_WRONLY | O_TRUNC | O_CREAT, 0666);
    if (fd == -1)
        throw SysError(format("opening file `%1%'") % path);
    writeFull(fd, (unsigned char *) s.c_str(), s.size());
+    if (doFsync) fdatasync(fd);
 }


@@ -297,8 +299,10 @@ static void _deletePath(const Path & path, unsigned long long & bytesFreed,
    if (lstat(path.c_str(), &st))
 	throw SysError(format("getting attributes of path `%1%'") % path);

-    bytesFreed += st.st_size;
-    blocksFreed += st.st_blocks;
+    if (!S_ISDIR(st.st_mode) && st.st_nlink == 1) {
+        bytesFreed += st.st_size;
+        blocksFreed += st.st_blocks;
+    }

    if (S_ISDIR(st.st_mode)) {
 	Strings names = readDirectory(path);
@@ -411,16 +415,6 @@ Paths createDirs(const Path & path)
 }


-void writeStringToFile(const Path & path, const string & s)
-{
-    AutoCloseFD fd(open(path.c_str(),
-        O_CREAT | O_EXCL | O_WRONLY, 0666));
-    if (fd == -1)
-        throw SysError(format("creating file `%1%'") % path);
-    writeFull(fd, (unsigned char *) s.c_str(), s.size());
-}
-
-
 LogType logType = ltPretty;
 Verbosity verbosity = lvlInfo;

@@ -1053,22 +1047,6 @@ string int2String(int n)
 }


-bool string2Int(const string & s, int & n)
-{
-    std::istringstream str(s);
-    str >> n;
-    return str && str.get() == EOF;
-}
-
-
-bool string2Int(const string & s, long long & n)
-{
-    std::istringstream str(s);
-    str >> n;
-    return str && str.get() == EOF;
-}
-
-
 bool hasSuffix(const string & s, const string & suffix)
 {
    return s.size() >= suffix.size() && string(s, s.size() - suffix.size()) == suffix;
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -1,6 +1,8 @@
 #ifndef __UTIL_H
 #define __UTIL_H

+#include "config.h"
+
 #include "types.hh"

 #include <sys/types.h>
@@ -8,6 +10,8 @@
 #include <unistd.h>
 #include <signal.h>

+#include <cstdio>
+

 namespace nix {

@@ -58,7 +62,7 @@ string readFile(int fd);
 string readFile(const Path & path);

 /* Write a string to a file. */
-void writeFile(const Path & path, const string & s);
+void writeFile(const Path & path, const string & s, bool doFsync = false);

 /* Read a line from a file descriptor. */
 string readLine(int fd);
@@ -89,10 +93,6 @@ Path createTempDir(const Path & tmpRoot = "", const Path & prefix = "nix",
   list of created directories, in order of creation. */
 Paths createDirs(const Path & path);

-/* Create a file and write the given text to it.  The file is written
-   in binary mode (i.e., no end-of-line conversions).  The path should
-   not already exist. */
-void writeStringToFile(const Path & path, const string & s);

 template<class T, class A>
 T singleton(const A & a)
@@ -295,9 +295,14 @@ bool statusOk(int status);


 /* Parse a string into an integer. */
+template<class N> bool string2Int(const string & s, N & n)
+{
+    std::istringstream str(s);
+    str >> n;
+    return str && str.get() == EOF;
+}
+
 string int2String(int n);
-bool string2Int(const string & s, int & n);
-bool string2Int(const string & s, long long & n);


 /* Return true iff `s' ends in `suffix'. */
--- a/src/nix-env/Makefile.am
+++ b/src/nix-env/Makefile.am
@@ -3,7 +3,7 @@ bin_PROGRAMS = nix-env
 nix_env_SOURCES = nix-env.cc profiles.cc profiles.hh help.txt
 nix_env_LDADD = ../libmain/libmain.la ../libexpr/libexpr.la \
 ../libstore/libstore.la ../libutil/libutil.la \
- ../boost/format/libformat.la ${bdb_lib} ${aterm_lib}
+ ../boost/format/libformat.la ${aterm_lib} @ADDITIONAL_NETWORK_LIBS@

 nix-env.o: help.txt.hh

@@ -11,6 +11,6 @@ nix-env.o: help.txt.hh
 	../bin2c/bin2c helpText < $< > $@ || (rm $@ && exit 1)

 AM_CXXFLAGS = \
- -I$(srcdir)/.. ${bdb_include} ${aterm_include} \
+ -I$(srcdir)/.. ${aterm_include} \
 -I$(srcdir)/../libutil -I$(srcdir)/../libstore \
 -I$(srcdir)/../libexpr -I$(srcdir)/../libmain -I../libexpr
--- a/src/nix-env/nix-env.cc
+++ b/src/nix-env/nix-env.cc
@@ -327,7 +327,7 @@ static bool createUserEnv(EvalState & state, DrvInfos & elems,
        makeBind(toATerm("derivations"),
            makeList(ATreverse(manifest)), makeNoPos()),
        makeBind(toATerm("manifest"),
-            makeStr(manifestFile, singleton<PathSet>(manifestFile)), makeNoPos())
+            makeStr(manifestFile, ATmakeList1(makeContextElem(toATerm(manifestFile), makeNull()))), makeNoPos())
        )));

    /* Instantiate it. */
@@ -704,52 +704,59 @@ static void upgradeDerivations(Globals & globals,
        foreach (DrvInfos::iterator, i, installedElems) {
            DrvName drvName(i->name);

-            MetaInfo meta = i->queryMetaInfo(globals.state);
-            if (keep(meta)) {
-                newElems.push_back(*i);
-                continue;
-            }
+            try {

-            /* Find the derivation in the input Nix expression with
-               the same name that satisfies the version constraints
-               specified by upgradeType.  If there are multiple
-               matches, take the one with the highest priority.  If
-               there are still multiple matches, take the one with the
-               highest version. */
-            DrvInfos::iterator bestElem = availElems.end();
-            DrvName bestName;
-            foreach (DrvInfos::iterator, j, availElems) {
-                DrvName newName(j->name);
-                if (newName.name == drvName.name) {
-                    int d = comparePriorities(globals.state, *i, *j);
-                    if (d == 0) d = compareVersions(drvName.version, newName.version);
-                    if ((upgradeType == utLt && d < 0) ||
-                        (upgradeType == utLeq && d <= 0) ||
-                        (upgradeType == utEq && d == 0) ||
-                        upgradeType == utAlways)
-                    {
-                        int d2 = -1;
-                        if (bestElem != availElems.end()) {
-                            d2 = comparePriorities(globals.state, *bestElem, *j);
-                            if (d2 == 0) d2 = compareVersions(bestName.version, newName.version);
-                        }
-                        if (d2 < 0) {
-                            bestElem = j;
-                            bestName = newName;
+                MetaInfo meta = i->queryMetaInfo(globals.state);
+                if (keep(meta)) {
+                    newElems.push_back(*i);
+                    continue;
+                }
+
+                /* Find the derivation in the input Nix expression
+                   with the same name that satisfies the version
+                   constraints specified by upgradeType.  If there are
+                   multiple matches, take the one with the highest
+                   priority.  If there are still multiple matches,
+                   take the one with the highest version. */
+                DrvInfos::iterator bestElem = availElems.end();
+                DrvName bestName;
+                foreach (DrvInfos::iterator, j, availElems) {
+                    DrvName newName(j->name);
+                    if (newName.name == drvName.name) {
+                        int d = comparePriorities(globals.state, *i, *j);
+                        if (d == 0) d = compareVersions(drvName.version, newName.version);
+                        if ((upgradeType == utLt && d < 0) ||
+                            (upgradeType == utLeq && d <= 0) ||
+                            (upgradeType == utEq && d == 0) ||
+                            upgradeType == utAlways)
+                        {
+                            int d2 = -1;
+                            if (bestElem != availElems.end()) {
+                                d2 = comparePriorities(globals.state, *bestElem, *j);
+                                if (d2 == 0) d2 = compareVersions(bestName.version, newName.version);
+                            }
+                            if (d2 < 0) {
+                                bestElem = j;
+                                bestName = newName;
+                            }
                        }
                    }
                }
-            }
+                
+                if (bestElem != availElems.end() &&
+                    i->queryOutPath(globals.state) !=
+                    bestElem->queryOutPath(globals.state))
+                {
+                    printMsg(lvlInfo,
+                        format("upgrading `%1%' to `%2%'")
+                        % i->name % bestElem->name);
+                    newElems.push_back(*bestElem);
+                } else newElems.push_back(*i);

-            if (bestElem != availElems.end() &&
-                i->queryOutPath(globals.state) !=
-                bestElem->queryOutPath(globals.state))
-            {
-                printMsg(lvlInfo,
-                    format("upgrading `%1%' to `%2%'")
-                    % i->name % bestElem->name);
-                newElems.push_back(*bestElem);
-            } else newElems.push_back(*i);
+            } catch (Error & e) {
+                e.addPrefix(format("while trying to find an upgrade for `%1%':\n") % i->name);
+                throw;
+            }
        }
    
        printMissing(globals.state, newElems);
--- a/src/nix-hash/Makefile.am
+++ b/src/nix-hash/Makefile.am
@@ -2,7 +2,7 @@ bin_PROGRAMS = nix-hash

 nix_hash_SOURCES = nix-hash.cc help.txt
 nix_hash_LDADD = ../libmain/libmain.la ../libstore/libstore.la ../libutil/libutil.la \
- ../boost/format/libformat.la ${bdb_lib} ${aterm_lib}
+ ../boost/format/libformat.la ${aterm_lib} @ADDITIONAL_NETWORK_LIBS@

 nix-hash.o: help.txt.hh

--- a/src/nix-instantiate/Makefile.am
+++ b/src/nix-instantiate/Makefile.am
@@ -3,7 +3,7 @@ bin_PROGRAMS = nix-instantiate
 nix_instantiate_SOURCES = nix-instantiate.cc help.txt
 nix_instantiate_LDADD = ../libmain/libmain.la ../libexpr/libexpr.la \
 ../libstore/libstore.la ../libutil/libutil.la \
- ../boost/format/libformat.la ${bdb_lib} ${aterm_lib}
+ ../boost/format/libformat.la ${aterm_lib} @ADDITIONAL_NETWORK_LIBS@

 nix-instantiate.o: help.txt.hh

@@ -11,6 +11,6 @@ nix-instantiate.o: help.txt.hh
 	../bin2c/bin2c helpText < $< > $@ || (rm $@ && exit 1)

 AM_CXXFLAGS = \
- ${bdb_include} ${aterm_include} \
+ ${aterm_include} \
 -I$(srcdir)/.. -I$(srcdir)/../libutil -I$(srcdir)/../libstore \
 -I$(srcdir)/../libexpr -I$(srcdir)/../libmain -I../libexpr
--- a/src/nix-instantiate/nix-instantiate.cc
+++ b/src/nix-instantiate/nix-instantiate.cc
@@ -40,7 +40,7 @@ static bool indirectRoot = false;
 static void printResult(EvalState & state, Expr e,
    bool evalOnly, bool xmlOutput, const ATermMap & autoArgs)
 {
-    PathSet context;
+    Context context;
    
    if (evalOnly)
        if (xmlOutput)
--- a/src/nix-store/Makefile.am
+++ b/src/nix-store/Makefile.am
@@ -2,7 +2,7 @@ bin_PROGRAMS = nix-store

 nix_store_SOURCES = nix-store.cc dotgraph.cc dotgraph.hh help.txt
 nix_store_LDADD = ../libmain/libmain.la ../libstore/libstore.la ../libutil/libutil.la \
- ../boost/format/libformat.la ${bdb_lib} ${aterm_lib}
+ ../boost/format/libformat.la ${aterm_lib} @ADDITIONAL_NETWORK_LIBS@

 nix-store.o: help.txt.hh

@@ -10,5 +10,5 @@ nix-store.o: help.txt.hh
 	../bin2c/bin2c helpText < $< > $@ || (rm $@ && exit 1)

 AM_CXXFLAGS = \
- -I$(srcdir)/.. ${bdb_include} $(aterm_include) -I$(srcdir)/../libutil \
+ -I$(srcdir)/.. $(aterm_include) -I$(srcdir)/../libutil \
 -I$(srcdir)/../libstore -I$(srcdir)/../libmain
--- a/src/nix-store/help.txt
+++ b/src/nix-store/help.txt
@@ -24,7 +24,6 @@ Operations:
  --import: import a path from a Nix archive, and register as 
      valid

-  --init: initialise the Nix database
  --verify: verify Nix structures
  --optimise: optimise the Nix store by hard-linking identical files

@@ -34,12 +33,14 @@ Operations:
 Query flags:

  --outputs: query the output paths of a Nix derivation (default)
-  --requisites / -R: print all paths necessary to realise a path
-  --references: print all paths referenced by the given path
-  --referrers: print all paths directly refering to the given path
-  --referrers-closure: print all paths (in)directly refering to the given path
-  --tree: print a tree showing the dependency graph of the given paths
-  --graph: print a dot graph rooted at given paths
+  --requisites / -R: print all paths necessary to realise the path
+  --references: print all paths referenced by the path
+  --referrers: print all paths directly refering to the path
+  --referrers-closure: print all paths (in)directly refering to the path
+  --tree: print a tree showing the dependency graph of the path
+  --graph: print a dot graph rooted at given path
+  --hash: print the SHA-256 hash of the contents of the path
+  --roots: print the garbage collector roots that point to the path

 Query switches (not applicable to all queries):

--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -165,41 +165,6 @@ static void opPrintFixedPath(Strings opFlags, Strings opArgs)
 }


-/* Place in `paths' the set of paths that are required to `realise'
-   the given store path, i.e., all paths necessary for valid
-   deployment of the path.  For a derivation, this is the union of
-   requisites of the inputs, plus the derivation; for other store
-   paths, it is the set of paths in the FS closure of the path.  If
-   `includeOutputs' is true, include the requisites of the output
-   paths of derivations as well.
-
-   Note that this function can be used to implement three different
-   deployment policies:
-
-   - Source deployment (when called on a derivation).
-   - Binary deployment (when called on an output path).
-   - Source/binary deployment (when called on a derivation with
-     `includeOutputs' set to true).
-*/
-static void storePathRequisites(const Path & storePath,
-    bool includeOutputs, PathSet & paths)
-{
-    computeFSClosure(storePath, paths);
-
-    if (includeOutputs) {
-        for (PathSet::iterator i = paths.begin();
-             i != paths.end(); ++i)
-            if (isDerivation(*i)) {
-                Derivation drv = derivationFromPath(*i);
-                for (DerivationOutputs::iterator j = drv.outputs.begin();
-                     j != drv.outputs.end(); ++j)
-                    if (store->isValidPath(j->second.path))
-                        computeFSClosure(j->second.path, paths);
-            }
-    }
-}
-
-
 static Path maybeUseOutput(const Path & storePath, bool useOutput, bool forceRealise)
 {
    if (forceRealise) realisePath(storePath);
@@ -261,14 +226,13 @@ static void opQuery(Strings opFlags, Strings opArgs)
 {
    enum { qOutputs, qRequisites, qReferences, qReferrers
         , qReferrersClosure, qDeriver, qBinding, qHash
-         , qTree, qGraph, qResolve } query = qOutputs;
+         , qTree, qGraph, qResolve, qRoots } query = qOutputs;
    bool useOutput = false;
    bool includeOutputs = false;
    bool forceRealise = false;
    string bindingName;

-    for (Strings::iterator i = opFlags.begin();
-         i != opFlags.end(); ++i)
+    foreach (Strings::iterator, i, opFlags)
        if (*i == "--outputs") query = qOutputs;
        else if (*i == "--requisites" || *i == "-R") query = qRequisites;
        else if (*i == "--references") query = qReferences;
@@ -286,6 +250,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
        else if (*i == "--tree") query = qTree;
        else if (*i == "--graph") query = qGraph;
        else if (*i == "--resolve") query = qResolve;
+        else if (*i == "--roots") query = qRoots;
        else if (*i == "--use-output" || *i == "-u") useOutput = true;
        else if (*i == "--force-realise" || *i == "-f") forceRealise = true;
        else if (*i == "--include-outputs") includeOutputs = true;
@@ -294,9 +259,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
    switch (query) {
        
        case qOutputs: {
-            for (Strings::iterator i = opArgs.begin();
-                 i != opArgs.end(); ++i)
-            {
+            foreach (Strings::iterator, i, opArgs) {
                *i = followLinksToStorePath(*i);
                if (forceRealise) realisePath(*i);
                Derivation drv = derivationFromPath(*i);
@@ -310,14 +273,11 @@ static void opQuery(Strings opFlags, Strings opArgs)
        case qReferrers:
        case qReferrersClosure: {
            PathSet paths;
-            for (Strings::iterator i = opArgs.begin();
-                 i != opArgs.end(); ++i)
-            {
+            foreach (Strings::iterator, i, opArgs) {
                Path path = maybeUseOutput(followLinksToStorePath(*i), useOutput, forceRealise);
-                if (query == qRequisites)
-                    storePathRequisites(path, includeOutputs, paths);
+                if (query == qRequisites) computeFSClosure(path, paths, false, includeOutputs);
                else if (query == qReferences) store->queryReferences(path, paths);
-                else if (query == qReferrers) store->queryReferrers(path,  paths);
+                else if (query == qReferrers) store->queryReferrers(path, paths);
                else if (query == qReferrersClosure) computeFSClosure(path, paths, true);
            }
            Paths sorted = topoSortPaths(paths);
@@ -328,9 +288,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
        }

        case qDeriver:
-            for (Strings::iterator i = opArgs.begin();
-                 i != opArgs.end(); ++i)
-            {
+            foreach (Strings::iterator, i, opArgs) {
                Path deriver = store->queryDeriver(followLinksToStorePath(*i));
                cout << format("%1%\n") %
                    (deriver == "" ? "unknown-deriver" : deriver);
@@ -338,9 +296,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
            break;

        case qBinding:
-            for (Strings::iterator i = opArgs.begin();
-                 i != opArgs.end(); ++i)
-            {
+            foreach (Strings::iterator, i, opArgs) {
                Path path = useDeriver(followLinksToStorePath(*i));
                Derivation drv = derivationFromPath(path);
                StringPairs::iterator j = drv.env.find(bindingName);
@@ -352,9 +308,7 @@ static void opQuery(Strings opFlags, Strings opArgs)
            break;

        case qHash:
-            for (Strings::iterator i = opArgs.begin();
-                 i != opArgs.end(); ++i)
-            {
+            foreach (Strings::iterator, i, opArgs) {
                Path path = maybeUseOutput(followLinksToStorePath(*i), useOutput, forceRealise);
                Hash hash = store->queryPathHash(path);
                assert(hash.type == htSHA256);
@@ -364,28 +318,37 @@ static void opQuery(Strings opFlags, Strings opArgs)

        case qTree: {
            PathSet done;
-            for (Strings::iterator i = opArgs.begin();
-                 i != opArgs.end(); ++i)
+            foreach (Strings::iterator, i, opArgs)
                printTree(followLinksToStorePath(*i), "", "", done);
            break;
        }
            
        case qGraph: {
            PathSet roots;
-            for (Strings::iterator i = opArgs.begin();
-                 i != opArgs.end(); ++i)
+            foreach (Strings::iterator, i, opArgs)
                roots.insert(maybeUseOutput(followLinksToStorePath(*i), useOutput, forceRealise));
 	    printDotGraph(roots);
            break;
        }

        case qResolve: {
-            for (Strings::iterator i = opArgs.begin();
-                 i != opArgs.end(); ++i)
+            foreach (Strings::iterator, i, opArgs)
                cout << format("%1%\n") % followLinksToStorePath(*i);
            break;
        }
            
+        case qRoots: {
+            PathSet referrers;
+            foreach (Strings::iterator, i, opArgs)
+                computeFSClosure(maybeUseOutput(followLinksToStorePath(*i), useOutput, forceRealise),
+                    referrers, true);
+            Roots roots = store->findRoots();
+            foreach (Roots::iterator, i, roots)
+                if (referrers.find(i->second) != referrers.end())
+                    cout << format("%1%\n") % i->first;
+            break;
+        }
+            
        default:
            abort();
    }
@@ -520,6 +483,7 @@ struct PrintFreed

 static void opGC(Strings opFlags, Strings opArgs)
 {
+    bool printRoots = false;
    GCOptions options;
    options.action = GCOptions::gcDeleteDead;
    
@@ -527,30 +491,33 @@ static void opGC(Strings opFlags, Strings opArgs)
    
    /* Do what? */
    foreach (Strings::iterator, i, opFlags)
-        if (*i == "--print-roots") options.action = GCOptions::gcReturnRoots;
+        if (*i == "--print-roots") printRoots = true;
        else if (*i == "--print-live") options.action = GCOptions::gcReturnLive;
        else if (*i == "--print-dead") options.action = GCOptions::gcReturnDead;
        else if (*i == "--delete") options.action = GCOptions::gcDeleteDead;
        else if (*i == "--max-freed") {
-            options.maxFreed = getIntArg(*i, i, opFlags.end());
-            if (options.maxFreed == 0) options.maxFreed = 1;
-        }
-        else if (*i == "--max-links") options.maxLinks = getIntArg(*i, i, opFlags.end());
-        else if (*i == "--use-atime") options.useAtime = true;
-        else if (*i == "--max-atime") {
-            options.useAtime = true;
-            options.maxAtime = getIntArg(*i, i, opFlags.end());
+            long long maxFreed = getIntArg<long long>(*i, i, opFlags.end());
+            options.maxFreed = maxFreed >= 1 ? maxFreed : 1;
        }
+        else if (*i == "--max-links") options.maxLinks = getIntArg<unsigned int>(*i, i, opFlags.end());
        else throw UsageError(format("bad sub-operation `%1%' in GC") % *i);

    if (!opArgs.empty()) throw UsageError("no arguments expected");
-    
-    PrintFreed freed(options.action == GCOptions::gcDeleteDead, results);
-    store->collectGarbage(options, results);

-    if (options.action != GCOptions::gcDeleteDead)
-        foreach (PathSet::iterator, i, results.paths)
-            cout << *i << std::endl;
+    if (printRoots) {
+        Roots roots = store->findRoots();
+        foreach (Roots::iterator, i, roots)
+            cout << i->first << " -> " << i->second << std::endl;
+    }
+
+    else {
+        PrintFreed freed(options.action == GCOptions::gcDeleteDead, results);
+        store->collectGarbage(options, results);
+
+        if (options.action != GCOptions::gcDeleteDead)
+            foreach (PathSet::iterator, i, results.paths)
+                cout << *i << std::endl;
+    }
 }


--- a/src/nix-worker/Makefile.am
+++ b/src/nix-worker/Makefile.am
@@ -2,7 +2,7 @@ bin_PROGRAMS = nix-worker

 nix_worker_SOURCES = nix-worker.cc help.txt
 nix_worker_LDADD = ../libmain/libmain.la ../libstore/libstore.la ../libutil/libutil.la \
- ../boost/format/libformat.la ${bdb_lib} ${aterm_lib}
+ ../boost/format/libformat.la ${aterm_lib} @ADDITIONAL_NETWORK_LIBS@

 nix-worker.o: help.txt.hh

@@ -10,5 +10,5 @@ nix-worker.o: help.txt.hh
 	../bin2c/bin2c helpText < $< > $@ || (rm $@ && exit 1)

 AM_CXXFLAGS = \
- -I$(srcdir)/.. ${bdb_include} $(aterm_include) -I$(srcdir)/../libutil \
+ -I$(srcdir)/.. $(aterm_include) -I$(srcdir)/../libutil \
 -I$(srcdir)/../libstore -I$(srcdir)/../libmain
--- a/src/nix-worker/nix-worker.cc
+++ b/src/nix-worker/nix-worker.cc
@@ -20,9 +20,18 @@
 using namespace nix;


+/* On platforms that have O_ASYNC, we can detect when a client
+   disconnects and immediately kill any ongoing builds.  On platforms
+   that lack it, we only notice the disconnection the next time we try
+   to write to the client.  So if you have a builder that never
+   generates output on stdout/stderr, the worker will never notice
+   that the client has disconnected until the builder terminates. */
+#ifdef O_ASYNC
+#define HAVE_HUP_NOTIFICATION
 #ifndef SIGPOLL
 #define SIGPOLL SIGIO
 #endif
+#endif


 static FdSource from(STDIN_FILENO);
@@ -90,7 +99,7 @@ static bool isFarSideClosed(int socket)


 /* A SIGPOLL signal is received when data is available on the client
-   communication scoket, or when the client has closed its side of the
+   communication socket, or when the client has closed its side of the
   socket.  This handler is enabled at precisely those moments in the
   protocol when we're doing work and the client is supposed to be
   quiet.  Thus, if we get a SIGPOLL signal, it means that the client
@@ -131,12 +140,14 @@ static void sigPollHandler(int sigNo)

 static void setSigPollAction(bool enable)
 {
+#ifdef HAVE_HUP_NOTIFICATION
    struct sigaction act, oact;
    act.sa_handler = enable ? sigPollHandler : SIG_IGN;
    sigfillset(&act.sa_mask);
    act.sa_flags = 0;
    if (sigaction(SIGPOLL, &act, &oact))
        throw SysError("setting handler for SIGPOLL");
+#endif
 }


@@ -453,8 +464,9 @@ static void performOp(unsigned int clientVersion,
        options.maxFreed = readLongLong(from);
        options.maxLinks = readInt(from);
        if (GET_PROTOCOL_MINOR(clientVersion) >= 5) {
-            options.useAtime = readInt(from);
-            options.maxAtime = readInt(from);
+            /* removed options */
+            readInt(from);
+            readInt(from);
        }

        GCResults results;
@@ -520,12 +532,14 @@ static void processConnection()
    myPid = getpid();    
    writeToStderr = tunnelStderr;

+#ifdef HAVE_HUP_NOTIFICATION
    /* Allow us to receive SIGPOLL for events on the client socket. */
    setSigPollAction(false);
    if (fcntl(from.fd, F_SETOWN, getpid()) == -1)
        throw SysError("F_SETOWN");
-    if (fcntl(from.fd, F_SETFL, fcntl(from.fd, F_GETFL, 0) | FASYNC) == -1)
+    if (fcntl(from.fd, F_SETFL, fcntl(from.fd, F_GETFL, 0) | O_ASYNC) == -1)
        throw SysError("F_SETFL");
+#endif

    /* Exchange the greeting. */
    unsigned int magic = readInt(from);
@@ -663,11 +677,12 @@ static void daemonLoop()
            AutoCloseFD remote = accept(fdSocket,
                (struct sockaddr *) &remoteAddr, &remoteAddrLen);
            checkInterrupt();
-            if (remote == -1)
+            if (remote == -1) {
 		if (errno == EINTR)
 		    continue;
 		else
 		    throw SysError("accepting connection");
+            }

            printMsg(lvlInfo, format("accepted connection %1%") % remote);

--- a/tests/init.sh
+++ b/tests/init.sh
@@ -36,12 +36,6 @@ ln -s $TOP/scripts/copy-from-other-stores.pl $NIX_BIN_DIR/nix/
 ln -s $TOP/scripts/download-using-manifests.pl $NIX_BIN_DIR/nix/
 ln -s $TOP/scripts/readmanifest.pm $NIX_BIN_DIR/nix/

-mkdir -p "$NIX_STATE_DIR"/manifests
-mkdir -p "$NIX_STATE_DIR"/gcroots
-mkdir -p "$NIX_STATE_DIR"/temproots
-mkdir -p "$NIX_STATE_DIR"/profiles
-ln -s "$NIX_STATE_DIR"/profiles "$NIX_STATE_DIR"/gcroots/
-
 cat > "$NIX_CONF_DIR"/nix.conf <<EOF
 gc-keep-outputs = false
 gc-keep-derivations = false
--- a/tests/lang/eval-okay-functionargs.exp.xml
+++ b/tests/lang/eval-okay-functionargs.exp.xml
@@ -0,0 +1,15 @@
+<?xml version='1.0' encoding='utf-8'?>
+<expr>
+  <list>
+    <string value="stdenv" />
+    <string value="fetchurl" />
+    <string value="aterm-stdenv" />
+    <string value="aterm-stdenv2" />
+    <string value="libX11" />
+    <string value="libXv" />
+    <string value="mplayer-stdenv2.libXv-libX11" />
+    <string value="mplayer-stdenv2.libXv-libX11_2" />
+    <string value="nix-stdenv-aterm-stdenv" />
+    <string value="nix-stdenv2-aterm2-stdenv2" />
+  </list>
+</expr>
--- a/tests/lang/eval-okay-functionargs.nix
+++ b/tests/lang/eval-okay-functionargs.nix
@@ -0,0 +1,80 @@
+let
+
+  stdenvFun = { }: { name = "stdenv"; };
+  stdenv2Fun = { }: { name = "stdenv2"; };
+  fetchurlFun = { stdenv }: assert stdenv.name == "stdenv"; { name = "fetchurl"; };
+  atermFun = { stdenv, fetchurl }: { name = "aterm-${stdenv.name}"; };
+  aterm2Fun = { stdenv, fetchurl }: { name = "aterm2-${stdenv.name}"; };
+  nixFun = { stdenv, fetchurl, aterm }: { name = "nix-${stdenv.name}-${aterm.name}"; };
+  
+  mplayerFun =
+    { stdenv, fetchurl, enableX11 ? false, xorg ? null, enableFoo ? true, foo ? null  }:
+    assert stdenv.name == "stdenv2";
+    assert enableX11 -> xorg.libXv.name == "libXv";
+    assert enableFoo -> foo != null;
+    { name = "mplayer-${stdenv.name}.${xorg.libXv.name}-${xorg.libX11.name}"; };
+
+  makeOverridable = f: origArgs: f origArgs //
+    { override = newArgs:
+        makeOverridable f (origArgs // (if builtins.isFunction newArgs then newArgs origArgs else newArgs));
+    };
+    
+  callPackage_ = pkgs: f: args:
+    makeOverridable f ((builtins.intersectAttrs (builtins.functionArgs f) pkgs) // args);
+
+  allPackages =
+    { overrides ? (pkgs: pkgsPrev: { }) }:
+    let
+      callPackage = callPackage_ pkgs;
+      pkgs = pkgsStd // (overrides pkgs pkgsStd);
+      pkgsStd = {
+        inherit pkgs;
+        stdenv = callPackage stdenvFun { };
+        stdenv2 = callPackage stdenv2Fun { };
+        fetchurl = callPackage fetchurlFun { };
+        aterm = callPackage atermFun { };
+        xorg = callPackage xorgFun { };
+        mplayer = callPackage mplayerFun { stdenv = pkgs.stdenv2; enableFoo = false; };
+        nix = callPackage nixFun { };
+      };
+    in pkgs;
+
+  libX11Fun = { stdenv, fetchurl }: { name = "libX11"; };
+  libX11_2Fun = { stdenv, fetchurl }: { name = "libX11_2"; };
+  libXvFun = { stdenv, fetchurl, libX11 }: { name = "libXv"; };
+  
+  xorgFun =
+    { pkgs }:
+    let callPackage = callPackage_ (pkgs // pkgs.xorg); in
+    {
+      libX11 = callPackage libX11Fun { };
+      libXv = callPackage libXvFun { };
+    };
+
+in
+
+let
+
+  pkgs = allPackages { };
+  
+  pkgs2 = allPackages {
+    overrides = pkgs: pkgsPrev: {
+      stdenv = pkgs.stdenv2;
+      nix = pkgsPrev.nix.override { aterm = aterm2Fun { inherit (pkgs) stdenv fetchurl; }; };
+      xorg = pkgsPrev.xorg // { libX11 = libX11_2Fun { inherit (pkgs) stdenv fetchurl; }; };
+    };
+  };
+  
+in
+
+  [ pkgs.stdenv.name
+    pkgs.fetchurl.name
+    pkgs.aterm.name
+    pkgs2.aterm.name
+    pkgs.xorg.libX11.name
+    pkgs.xorg.libXv.name
+    pkgs.mplayer.name
+    pkgs2.mplayer.name
+    pkgs.nix.name
+    pkgs2.nix.name
+  ]
--- a/2
+++ b/2
@@ -1 +1 @@
-0.13
+0.14
Author	SHA1	Message	Date
Eelco Dolstra	29fd60131b	* Add a primop to return the context of a string.	2010-01-31 20:54:44 +00:00
Eelco Dolstra	6d1abdc6d9	* In string contexts containing derivations (e.g. "${somePkg}/bin/foo"), store the original derivation expression in the context.	2010-01-31 20:08:57 +00:00
Eelco Dolstra	25fc95d56d		2010-01-31 20:06:58 +00:00
Eelco Dolstra	07ffdc2862	* Added an option "fsync-metadata" to fsync() changes to /nix/var/nix/db. * Removed the function writeStringToFile since it does (almost) the same thing as writeFile.	2010-01-29 12:22:58 +00:00
Eelco Dolstra	ad529fb89f	* Don't consider a store path valid if its info file exists but is zero bytes long. That makes Nix more robust in case of crashes (especially on ext4).	2010-01-29 11:53:58 +00:00
Eelco Dolstra	fdcaf37361	* Made `nix-store -qR --include-outputs' much faster if there are multiple paths specified on the command line (from O(n * m) to O(n + m), where n is the number of arguments and m is the size of the closure).	2010-01-25 17:18:44 +00:00
Eelco Dolstra	50e34891f0	* Disable gzip compression in build-remote.pl because it puts too much load on the Hydra build farm (where it's unnecessary anyway because it has a fast connection to the build machines). In any case, compression can be enabled by using the `-C' option to ssh.	2010-01-25 16:14:45 +00:00
Eelco Dolstra	5388944e8d	* Make the garbage collector do the right thing when `gc-keep-outputs' is enabled by not depending on the deriver.	2010-01-25 16:04:32 +00:00
Eelco Dolstra	f0c0277970	* On startup, set the default SIGCHLD handler. This is so that Nix works correctly in weird environments where the SIGCHLD handler is set to "ignore".	2010-01-12 12:22:38 +00:00
Eelco Dolstra	ef92a14bfe	* Include config.h before the C library headers, because it defines _FILE_OFFSET_BITS=64. Without it, functions like stat() fail on large file sizes. This happened with a Nix store on squashfs: $ nix-store --dump /tmp/mnt/46wzqnk4cbdwh1dclhrpqnnz1icak6n7-local-net-cmds > /dev/null error: getting attributes of path `/tmp/mnt/46wzqnk4cbdwh1dclhrpqnnz1icak6n7-local-net-cmds': Value too large for defined data type $ stat /tmp/mnt/46wzqnk4cbdwh1dclhrpqnnz1icak6n7-local-net-cmds File: `/tmp/mnt/46wzqnk4cbdwh1dclhrpqnnz1icak6n7-local-net-cmds' Size: 0 Blocks: 36028797018963968 IO Block: 1024 regular empty file (This is a bug in squashfs or mksquashfs, but it shouldn't cause Nix to fail.)	2009-12-17 14:12:44 +00:00
Eelco Dolstra	945d8218fb	* Build correctly against newer ATerm releases. Fixes "error: 'union' tag used in naming 'struct _ATerm'".	2009-12-16 15:29:50 +00:00
Eelco Dolstra	d8a5dc02fc	* Build on Fedora 12.	2009-12-10 13:14:22 +00:00
Eelco Dolstra	3a78af1e24	* Release notes.	2009-12-09 21:02:24 +00:00
Eelco Dolstra	7ca9972636	* When doing a nix-pull, remove old manifests downloaded from the same URL. This prevents lots of old cruft accumulating in /nix/var/nix/manifests.	2009-12-09 19:36:54 +00:00
Eelco Dolstra	c4c84d1edb	* nix-build: be less verbose.	2009-12-09 18:08:28 +00:00
Eelco Dolstra	bcd6cdf0d8	* Give a better error message when trying to build something and readOnlyMode is set.	2009-12-09 17:45:22 +00:00
Eelco Dolstra	13618b191e	* Grrr.	2009-11-24 13:28:46 +00:00
Eelco Dolstra	aa5a768720	* GCC 4.4 is stricter about the EOF macro (http://hydra.nixos.org/build/156340).	2009-11-24 12:56:26 +00:00
Eelco Dolstra	9b8fda796b	* Templatise getIntArg / string2Int.	2009-11-24 12:26:25 +00:00
Eelco Dolstra	8022015552	* In the garbage collector, don't count files with a link count > 1 in the "bytes/blocks freed" statistics.	2009-11-24 10:51:52 +00:00
Eelco Dolstra	f9e766db98	* Randomise the order in which we delete entries to make the collector less biased towards deleting paths that come alphabetically first (e.g. /nix/store/000...). This matters when using --max-freed etc.	2009-11-24 09:53:18 +00:00
Eelco Dolstra	ca50c83fbb		2009-11-23 21:21:29 +00:00
Eelco Dolstra	3d55f1eb57	* A command `nix-store --query --roots <paths>' to find the garbage collector roots that point (directly or indirectly) to the given paths.	2009-11-23 18:16:25 +00:00
Eelco Dolstra	ae6bf87273	* `nix-store --gc --print-roots': also print the path of the actual root symlink, not just its target. E.g.: /nix/var/nix/profiles/system-99-link -> /nix/store/76kwf88657nq7wgk1hx3l1z5q91zb9wd-system	2009-11-23 17:23:12 +00:00
Eelco Dolstra	c364d5d1e3	* Made the garbage collector a lot faster. It no longer computes the complete set of live and dead paths before starting the actual deletion, but determines liveness on demand. I.e. for any path in the store, it first tries to delete all the referrers, and then the path itself. This means that the collector can start deleting paths almost immediately.	2009-11-23 16:34:24 +00:00
Eelco Dolstra	4f7e5f5810	* Don't create /nix/var/nix/gcroots/{tmp,channels}, since they don't seem to be used anymore.	2009-11-23 12:48:54 +00:00
Eelco Dolstra	8824d60fe5	* Remove the --use-atime / --max-atime garbage collector flags. Many (Linux) machines no longer maintain the atime because it's too expensive, and on the machines where --use-atime is useful (like the buildfarm), reading the atimes on the entire Nix store takes way too much time to make it practical.	2009-11-20 17:12:38 +00:00
Eelco Dolstra	997db91e07	* Don't pass -K. It should really inherit the setting of the calling Nix though.	2009-11-17 16:22:39 +00:00
Eelco Dolstra	3392d32e8b	* In nix-pull/nix-channel, create the manifests directory if it doesn't exist. The Debian packages don't include the manifests directory, so nix-channel would silently skip doing a nix-pull, resulting in everything being built from source. Thanks to Juan Pedro Bolívar Puente.	2009-11-13 10:08:31 +00:00
Eelco Dolstra	327a232c85	* Remove support for old (before Nix 0.12pre12020) databases.	2009-11-06 01:15:44 +00:00
Eelco Dolstra	c60d796f04	* Version bump.	2009-11-05 22:23:38 +00:00
Eelco Dolstra	e8bad77c7c		2009-11-05 15:20:19 +00:00
Eelco Dolstra	7680904839	* Build on Karmic.	2009-11-05 14:53:01 +00:00
Eelco Dolstra	58f3338bfa	* The Nix .deb package depends on curl.	2009-11-05 14:40:42 +00:00
Eelco Dolstra	268d90a03e	* Various updates.	2009-11-05 09:07:43 +00:00
Eelco Dolstra	1ff8758f76	* Manual updates.	2009-11-04 16:52:35 +00:00
Eelco Dolstra	8520542071	* When building in a chroot, make a copy of a file if hard-linking fails. This is likely to happen after a `nix-store --optimise', because some files may have 32000 links (NIX-111).	2009-10-22 08:28:33 +00:00
Eelco Dolstra	6b9f6b0222	* Remove a prototype for a function that no longer exists.	2009-10-22 08:12:38 +00:00
Eelco Dolstra	deb342fb08	* builtins.trace: in the common case that the value is a string, then show the string, not the ATerm, so we get `trace: bla' instead of `trace: Str("bla",[])'.	2009-10-22 08:10:12 +00:00
Eelco Dolstra	437077c39d	* Added a primop unsafeDiscardOutputDependency needed by Disnix to pass derivation paths to a builder without actually building them.	2009-10-21 15:05:30 +00:00
Eelco Dolstra	6f7d7bc1de	* Give a useful error message when an evaluation error occurs while trying to upgrade a package.	2009-10-13 09:30:17 +00:00
Sander van der Burg	53a4981fa2	Added optional parameter which adds -lnsl -lsocket to make the Nix package manager work on OpenSolaris	2009-10-08 14:50:37 +00:00
Peter Simons	18f0ff003d	configure.ac: use AC_SYS_LARGEFILE to determine how to enable 64-bit file size support Defining -D_FILE_OFFSET_BITS=64 works on most platforms, but not on all (i.e. Solaris). Also, the Autoconf macro offers the user a switch to disable the functionality in case of problems.	2009-10-06 09:14:06 +00:00
Eelco Dolstra	96f1517831	* Support platforms that don't have O_ASYNC (e.g. OpenSolaris apparently).	2009-09-30 11:32:04 +00:00
Eelco Dolstra	1a8f8fd86f	* OpenSolaris compatibility.	2009-09-30 09:54:29 +00:00
Eelco Dolstra	0f79ad47c5		2009-09-25 12:36:03 +00:00
Eelco Dolstra	c7057fc1f2	* And some more.	2009-09-24 07:39:55 +00:00
Eelco Dolstra	193f59e077	* Fix a build failure on Fedora 11. rename() needs <stdio.h>.	2009-09-24 07:21:29 +00:00
Eelco Dolstra	0ae2be5692		2009-09-24 07:05:06 +00:00
Eelco Dolstra	1332dd1ed3	* tryEval shouldn't catch all exceptions of type Error, since not all of them leave the evaluator in a continuable state. Also, it should be less chatty.	2009-09-23 19:19:26 +00:00
Eelco Dolstra	63a17d4bd5	* Don't build against BDB on Cygwin, it's been broken for unknown reasons for a while (e.g. http://hydra.nixos.org/build/79164).	2009-09-23 18:52:18 +00:00
Eelco Dolstra	676e07902e	* Darwin hack.	2009-09-23 18:04:55 +00:00
Eelco Dolstra	64e89980e8	* Create some state directories automatically as a convenience.	2009-09-23 17:05:51 +00:00
Rob Vermaas	48b58617e9	* include wait.h for WEXITSTATUS	2009-09-23 12:57:15 +00:00
Eelco Dolstra	51ad64cc07	* Use xmllint (>= 2.7.4) for RelaxNG validation instead of Jing.	2009-09-18 11:45:56 +00:00
Eelco Dolstra	df05a759e4	* In "make init-state", ignore errors creating /nix/store. Hack to get the Debian VM builds to work (where /nix/store is a mount point containing the store of the host).	2009-09-18 11:01:30 +00:00
Eelco Dolstra	d3de71efc9		2009-09-17 17:44:13 +00:00
Eelco Dolstra	e1df4ef73c		2009-09-17 17:02:14 +00:00
Eelco Dolstra	86408b3f47	* build-remote.pl: Pick machines in a round-robin order, rather than giving jobs to the first machine until it hits its job limit, then the second machine and so on. This should improve utilisation of the Hydra build farm a lot. Also take an optional speed factor into account to cause fast machines to be preferred over slower machines with a similar load.	2009-09-17 15:48:17 +00:00
Eelco Dolstra	57e0d73c77	* build-remote.pl: allow the system type to be a comma-separated list of system types. Don't treat the x86_64-linux system type specially.	2009-09-17 13:51:04 +00:00
Eelco Dolstra	0dbd4638e0	* Two primops: builtins.intersectAttrs and builtins.functionArgs. intersectAttrs returns the (right-biased) intersection between two attribute sets, e.g. every attribute from the second set that also exists in the first. functionArgs returns the set of attributes expected by a function. The main goal of these is to allow the elimination of most of all-packages.nix. Most package instantiations in all-packages.nix have this form: foo = import ./foo.nix { inherit a b c; }; With intersectAttrs and functionArgs, this can be written as: foo = callPackage (import ./foo.nix) { }; where callPackage = f: args: f ((builtins.intersectAttrs (builtins.functionArgs f) pkgs) // args); I.e., foo.nix is called with all attributes from "pkgs" that it actually needs (e.g., pkgs.a, pkgs.b and pkgs.c). (callPackage can do any other generic package-level stuff we might want, such as applying makeOverridable.) Of course, the automatically supplied arguments can be overriden if needed, e.g. foo = callPackage (import ./foo.nix) { c = c_version_2; }; but for the vast majority of packages, this won't be needed. The advantages are to reduce the amount of typing needed to add a dependency (from three sites to two), and to reduce the number of trivial commits to all-packages.nix. For the former, there have been two previous attempts: - Use "args: with args;" in the package's function definition. This however obscures the actual expected arguments of a function, which is very bad. - Use "{ arg1, arg2, ... }:" in the package's function definition (i.e. use the ellipis "..." to allow arbitrary additional arguments), and then call the function with all of "pkgs" as an argument. But this inhibits error detection if you call it with an misspelled (or obsolete) argument.	2009-09-15 13:01:46 +00:00
Michael Raskin	3bca8931e8	Adding tryEval builtin. It allows to catch presence of errors in an expression.	2009-08-25 16:06:46 +00:00
Eelco Dolstra	5e9a4e5101		2009-08-03 13:32:13 +00:00
Eelco Dolstra	9b46d1ae6f		2009-08-03 12:24:20 +00:00
Eelco Dolstra	20b6f94b65	* nix-build: pass the --show-trace flag.	2009-07-15 09:10:38 +00:00
Eelco Dolstra	d413612029	* Remove the redundant <sections> around refentries.	2009-07-14 14:58:12 +00:00
Eelco Dolstra	1f169f43b3	* Leave out the collaborators / revision history page.	2009-07-10 13:42:12 +00:00
Eelco Dolstra	5e2e2f10ef		2009-07-10 11:48:49 +00:00
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